West Sussex on Wikipedia.

Albourne, St. Bartholomew on Church Lane. TQ 257 162. © Tony Preston. Link. Grade II listed.
Aldingbourne, St. Mary the Virgin. © David and Pat Halliday.
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 307 309. © Kevin Gordon. Link.
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. © Phil Jobson. 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. Link1. Link2.
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 908 075. © 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, both © 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 299 140. © Tony Preston. Link.
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.

Duncton, Holy Trinity. Another view, and an interior view. All © Gervase N. E. Charmley (2012). Link.

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). From an old postcard in Reg Dossell's Collection. A modern view, and two interior views - 1, 2, all © Charles Clegg (2012). 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. From an old postcard in Steve Bulman's Collection.
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. © Christopher Skottowe (1962). Link. Grade I listed.
Shoreham-by-Sea, St. Mary. From an old postcard in Steve Bulman's Collection. Another old postcard view, this one from Reg Dossell's Collection. Link.
Slaugham, St. Mary. From an old postcard (where the text says Slaughan), Bulman 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). 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.
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, and the interior. 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. From an old postcard in Reg Dosell's Collection. 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.