West Sussex on Wikipedia.

Albourne, St. Bartholomew on Church Lane. TQ 257 162. © Tony Preston. Link. Grade II listed.
Aldingbourne, St. Mary the Virgin. SU 9233 0548. © David and Pat Halliday. The font, © Christopher Skottowe (1962). Link. Grade I listed.
Amberley, St. Michael and All Angels on Church Street - the splendid chancel arch. © Christopher Skottowe (1961). Link, which has exterior photos. The very short grade I listing.
Angmering, St. Margaret. TQ 067 043. From a postcard in the Kevin Gordon Collection. Link.
Ardingly, St. Peter. TQ 339 298. © Kevin Gordon. Link.
Arundel.

Balcombe, St. Mary. TQ 3070 3091. © Kevin Gordon. Another view, and the interior, both © Chris Kippin (2022). Link. Grade I listed (ignore the photo!). Bramble Hall on Bramble Hill is, or stands on the site of, a Congregational Church. TQ 3089 3060. © Chris Kippin (2022).
Barnham, St. Mary the Virgin. A close-up of the church. From an old postcard in Steve Bulman's Collection. Previously in the Unknown section, thanks to Noel Walley for identifying this church. Link.
Billingshurst.
Bognor Regis, St. Mary Magdalene at South Bersted. Previously in the "Unknown" section, my thanks to Phil Draper for the identification. From Steve Bulman's Collection. Link1. Link2. Another Bognor mystery was sent in by Peter Boyce who wanted to learn where this painting was produced. It's by R. O. Dunlop R.A. whose floruit was in the 1950's and 1960's. He lived near Chichester, and painted widely in Sussex and further afield in southern England. Colin Waters identified the painting on this website, and it is called "Old Street, Bognor". Unfortunately, there isn't a thoroughfare called Old Street in Bognor, so this is just a generic old street. In a fine piece of detective work, Tony Preston has also been looking into this church. He points out that the website included earlier in this entry also has an image of a page from a magazine, wherein the painting is shown, with the title Old Bognor Street, rather than Old Street, Bognor, supporting my assumption that Old Street as such doesn't exist. It also includes a hand-written date of 1956 for the painting. He has sent a link (here) to a website describing the church of St. John the Baptist, built in 1821, with a tower added circa 1834. The church itself was demolished 1891, but the tower was left standing until 1961 (i.e. after the painting was made). This link shows two postcards (scroll down) of Waterloo Gardens, both showing the church in the background, a good match for the painting. An old map shows St. John the Baptist's tower standing on Market Street, and comparing the painting with the map, I suspect that the view is from what was then Chapel Street, to the north of Market Street. Note that Chapel Street has since been re-routed from its original course. [Peter - the email address I have for you is invalid, so I hope you see this].
Bolney, St. Mary Magdalene. TQ 261 226. From an old postcard in Steve Bulman's Collection. A modern view. © Kevin Gordon. Link. Village Chapel (CoE). TQ 263 235. © Kevin Gordon. Link.
Bosham, Holy Trinity. SU 8042 0388. © Phil Jobson. A 2019 Streetview provides another view. Previously in the Unknown section, John Bowdler was looking for the location of this font. Though the postcard offered no clues, Simon Davies managed to identify it as belonging to Holy Trinity. Link. Grade I listed. The former U.R.C. (originally Congregational) stands on Bosham Lane, at SU 8050 0412. It has a date-stone for 1837, and was seen by Streetview in 2021. Grade II listed.
Boxgrove, St. Mary & St. Blaise. The church now serving as the parish church was originally only a part of the much larger Priory, the ruins of which are also visible in this old postcard from Steve Bulman's Collection. A modern view. SU 9083 0751. © Kevin Gordon. Four interior photos - 1, 2, 3, 4, the latter showing the De La Warr chantry. All © Christopher Skottowe (1961). Link1. Link2. The remains of the Priory nave and chapter house, and a column capital, all  © Christopher Skottowe (1961). Link. The very brief Grade I listing.
Bramber, St. Nicholas. An inside view. Both from old postcards, Brett Jeffery's Collection. Link.
Broadwater, St. Mary. From an old postcard in Steve Bulman's Collection. A modern view. © Graeme Harvey. Link.
Buncton, All Saints. According to the Wikipedia entry, a sheela-na-gig carving here was destroyed by vandals in 2004. From an old postcard in Steve Bulman's Collection. Two additional views - 1, 2, both © Christopher Skottowe (1961). Link. Grade I listed.
Burgess Hill, St. John the Evangelist (1861-3) on Lower Church Road. TQ 312 192. Link. Grade II* listed. St. Andrew on Cants Lane. Another view. TQ 321 196. Link. King's Church at The King's Centre on Victoria Road. It was converted from a warehouse. TQ 304 189. Link. All Saints U.R.C. on Junction Road. TQ 318 189. Link. All © Tony Preston (2016).
Bury, St. John the Evangelist. From an old postcard in Geoff Watts Collection. Link.

Chichester.
Church Norton, St. Wilfrid. SZ 872 958. From an old postcard, Kevin Gordon's Collection. A modern view. © Kit Heald. Link.
Clayton, St. John the Baptist. TQ 2991 1397. © Tony Preston. Interior view, © Christopher Skottowe (1963). Link. Grade I listed.
Climping, St. Mary. TQ 003 026. From the postcard collection of Kevin Gordon. Link.
Compton, St. Mary. © Juile Brutnell.
Crawley, St. Michael & All Angels (currently closed). © Peter Morgan. St. John the Baptist. From an old postcard (franked 1904) in Steve Bulman's Collection. Link. Islamic Centre and Mosque on London Road, Langley Green. TQ 270 385. © Mehmood Naqshbandi, and reproduced from his website Muslims in Britain.
Cuckfield, Holy Trinity. TQ 303 244. © Kevin Gordon. Link.

Didling, St Andrew, as seen (distantly) by Streetview in 2011. SU 8350 1812. The Saxon font, © Christopher Skottowe (1962). Link1. It contains a link to a video tour. Link2. Grade I listed.
Duncton, Holy Trinity. Another view, and an interior view. SU 9607 1752. All © Gervase N. E. Charmley (2012). Link. Grade II listed. St. Anthony and St. George (R.C.) as seen by Streetview in 2011. Link. Grade II listed. St. Richard stands in Burton Park, east of the village, at SU 9675 1755. The dedication is a recent one (2003), according to Wikipedia), older sources saying the original dedication (if it had one) was lost. The tomb of a lady, and the early font. All © Christopher Skottowe (1962). Link. For a grade I listing, it's a short entry.

Eartham, St. Margaret. SU 938 093. © Kevin Gordon. Link.
Easebourne, St. Mary. From an old postcard in Paul E. Barnett's Collection. Link. Grade I listed.
East Grinstead, St. Swithun. From an old postcard (where it's spelled Swithin), franked in 1919, in Steve Bulman's Collection. Link.
Edburton, St. Andrew. TQ 233 115. © Tony Preston (2016). Link1. Link2.

Ferring, St. Andrew. TQ 094 026. From a postcard in the Kevin Gordon Collection. Link.
Findon, St. John the Baptist. From an old postcard in Reg Dosell's Collection. Link.
Fittleworth, St. Mary. From an old postcard in Geoff Watt's Collection.
Forestside, Christ Church. © Julie Brutnell. Link.

Goring-by-Sea, St. Mary. TQ 111 026. From a postcard in the Kevin Gordon Collection. Link.

Hardham, St. Botulph, which Kevin says has exceptional wall paintings. TQ 039 176. © Kevin Gordon. Link.
Hassocks, U.R.C. on Keymer Road. TQ 307 155. © Tony Preston. Link.
Haywards Heath, St. Wilfred. From an old postcard in Steve Bulman's Collection. Methodist Church. TQ 331 244. © Dave Westrap. Link.
Heyshott, St. James. Another view. Both from old postcards in Reg Dosell's Collection. Link.
Highbrook, All Saints. From an old postcard in Steve Bulman's Collection. Link.
Horsham.
Horsted Keynes, St. Giles. From a 19th century engraving, courtesy of the Colin Waters Collection. An old postcard view, from Reg Dosell's Collection. Link.
Hurstierpoint.

Ifield, St. Margaret. TQ 247 376. From an old postcard in Steve Bulman's Collection.
Itchingfield, St. Nicholas (open most days). TQ 1314 2894. From an old postcard in Reg Dossell's Collection. A modern view, and two interior views - 1, 2, all © Charles Clegg (2012). The font, © Christopher Skottowe (1963). Link. Grade II* listed. In the churchyard is a C15 priest's house, which is also grade II* listed. Another view. Both © Christopher Skottowe (1963). Link.

Keymer, St Cosmas and St Damian on Keymer Road. TQ 315 153.  Link. Grade II listed. St. Edward the Confessor (R.C.) on Lodge Lane. TQ 313 153. Link. Both © Tony Preston.

Lindfield, All Saints. TQ 3489 2585. From an old postcard in Steve Bulman's Collection. Another old postcard shows the interior - from Christopher Skottowe's Collection. Link. Grade II* listed.
Littlehampton, St. Mary. From an old postcard in Steve Bulman's Collection.
Lyminster, St. Mary Magdalene. TQ 023 048. From the postcard collection of Kevin Gordon. Link.

Midhurst, St. Mary Magdalen and St. Denys. SU 887 215. From the postcard collection of Kevin Gordon. An old postcard view, from Reg Dosell's Collection. Link. Divine Motherhood and St Francis of Assisi (R.C.). Another view. Both © Christopher Skottowe (1961). Link.
Milland, St. Luke. From an old postcard in Steve Bulman's Collection. Link.

Newtimber St. John the Evangelist. TQ 272 135. © Tony Preston (2016). Link. Grade II* listed.

Parham, St. Peter. From an old postcard (franked 1905), Bulman Collection. Link.
Petworth.
Poynings, Holy Trinity. TQ 265 121. © Tony Preston (2016). Link1. Link2. Grade I listed.
Pulborough, St. Mary. Another view. TQ 047 187. Both © Steve Taylor. Link. St. Crispin & St. Crispinian (R.C.). Another view. TQ 046 188. Both © Steve Taylor. Link (very slow when I tested). U.R.C. Built as the hall for the Congregational Church in 1947, the congregation now worships here, and the church has been sold. © Gervase N. E. Charmley (2012).
Pyecombe, Church of the Transfiguration. TQ 292 126. © Tony Preston (2016). Link. Grade I listing, which says the dedication is unknown.

Rogate, St. Bartholomew. From an old postcard in Steve Bulman's Collection.

Sayers Common, Christ Church on Oakhurst. TQ 269 135. © Tony Preston. Link.
Selham, St. James. SU 933 207. From the postcard collection of Kevin Gordon. Link.
Selsey, the Chapel of St. Wilfrid at Church Norton. SZ 872 957. From a postcard in the Kevin Gordon Collection. Link. St. Peter. From an old postcard in Reg Dosell's Collection. Link.
Shipley, St. Mary the Virgin. Another view, the porch, and tomb of  Sir Thomas Caryll (d. 1616). TQ 1449 2181. All © Christopher Skottowe (various dates). At the time of Christopher's visit, the church was home to a medieval reliquary, which this source dates to the 13th century, from Limoges. Stolen in 1976, and later recovered, it's now in Horsham Museum. A photo here shows a different face - the museum has confirmed to Christopher that it is the same item. © Christopher Skottowe (1963). Link. Grade I listed.
Shoreham-by-Sea, St. Mary de Haura. TQ 2162 0512. From an old postcard in Steve Bulman's Collection. Another old postcard view, this one from Reg Dossell's Collection. Link. Grade I listed.
Slaugham, St. Mary. From an old postcard (where the text says Slaughan), in Steve Bulman's Collection. The scanned image had to be heavily processed to get even this poor quality image. Link.
Slindon, St. Mary. SU 961 083. © Kevin Gordon. The font, © Christopher Skottowe (1961). Link. Grade I listed.
Slinfold, U.R.C., built as Congregational in 1878. © Gervase N. E. Charmley (2012).
Sompting, St. Mary the Blessed Virgin. Simon describes the spire as "Rhenish helm", which is confirmed in Betjeman, who adds that it is unique in England. © Simon Kidner. A view from the 1930's. Illustration from the Colin Waters Collection. Another view, © Christopher Skottowe (1964), and an old postcard view, from his collection. Link. Grade I listed.
Steyning, St. Andrew and St. Cuthman on Vicarage Lane. TQ 179 114. From the postcard collection of Kevin Gordon. Another view, © Tony Preston. Link. Grade I listed. Christ the King (R.C.) on Bramber Road. Another view. TQ 178 108. Both © Tony Preston. Methodist Church on High Street. TQ 178 112. © Tony Preston.
Storrington, St. Mary. From an old postcard (franked 1905), Bulman Collection.
Sullington, St. Mary. From an old postcard in Steve Bulman's Collection. Link1. Link2.

Tangmere, St. Andrew. From an old postcard in Steve Bulman's Collection. Link.
Terwick, St. Peter. From an old postcard in Steve Bulman's Collection. Link.
Tortington, St. Mary Magdalene, as seen (distantly) by Streetview in 2009. It's now in the care of the Churches Conservation Trust. The south doorway, and the font, both © Christopher Skottowe. TQ 0030 0498. Link. Grade II listed.
Trotton, St. George. From an old postcard in Steve Bulman's Collection. Link.
Twineham, St. Peter on Church Lane off Twineham Lane. TQ 253 200. © Tony Preston. Link. Grade I listed.

Up Marden, St. Michael & All Angels. SU 795 142. © Kevin Gordon. Link.
Upwaltham, St. Mary. Another view, and an interior view. All © Gervase N. E. Charmley (2012). Link.

Warminghurst, Holy Sepulchre. Another view, the interior and pulpit. All © Christopher Skottowe (1961). Link. Grade I listed.
West Dean, St. Andrew. From an old postcard in Reg Dosell's Collection.
West Grinstead, St. George. TQ 1708 2068. From an old postcard in Reg Dosell's Collection. Two more views - 1, 2, the porch, and the tomb of William Powlett (d. 1746), all © Christopher Skottowe (1963). Link1. Link2. Grade I listed. Shrine of Our Lady of Consolation (R.C.), as seen by Streetview in 2019. TQ 1771 2116. Link.
West Itchenor, St. Nicholas. © Juile Brutnell.
West Thorney, St. Nicholas. From an old postcard, Geoff Watt's Collection. Link1. Link2.
Wisborough Green, St. Peter ad Vincula. TQ 052 259. From a postcard in the Kevin Gordon Collection. Link.
Worth, St. Nicholas. TQ 302 362. © Rick Williams. Link.
Worthing, Goring U.R.C. on Barrington Road. © Adam Schofield (2014). Link.