My knowledge of the divisions of London is rather vague. If a church is wrongly listed here, please let me know!

Westminster on Wikipedia.
 

Churches in Soho (opens another page).

All Souls, Langham Place, consecrated in 1824. © Bill McKenzie. Another view. An information board gives a little history. Both © Dennis Harper (2012). Link.

Cathedral of the Dormition of the Mother of God and All Saints (Russian Orthodox) on Ennismore Gardens. Built as All Saints (1848-9 until 1955). TQ 2718 7956. © Martin Richter (2012). Link1. Link2 (excellent history). Grade II* listed.

The former Christ Church, Lancaster Gate. According to this link, the main body of the church was demolished in 1978, leaving only the tower and spire. From an old postcard in Reg Dosell's Collection.

Deutsche Evangelische Christuskirche on Montpelier Place, consecrated in 1904. Another view. TQ 2737 7945. Both © Martin Richter (2012). Link1. Link2 (with much interesting and surprising history). Link3. Link4. Link5.

Emmanuel Evangelical Church on Marsham Street. TQ 2996 7916. © Gerard Charmley. Grade II* listing which explains that it was built in 1926-30 as a Christian Science Church and Sunday School Chapel (Ninth Church of Christian Scientist), which it remained until 1997 -see here and here. Emmanuel took up residence in the same year - see here.

Methodist Central Hall, © Bill McKenzie.

Notre Dame de France (French Catholic) on Leicester Place. © Gervase N. E. Charmley. Link.

Our Lady of the Assumption and St. Gregory (R.C., 1790), on Warwick Street - interior view. Another interior. Both © Mike Forbester. Link.

Sacred Heart (R.C.) on Horseferry Road. A minor mystery here - Genuki says it was previously Wesleyan Methodist, while this website says it was built in 1962, which makes the Wesleyan attribution unlikely. The usually reliable Pevsner supports the latter. Pevsner also says that it replaced a chapel-of-ease to Westminster Cathedral, and that it was bombed in WWII. Had this been Wesleyan originally? Another view. TQ 2975 7903. Both © Chris Kippin (2018). Since I posted this entry, Chris has been back in touch to supply a little history. Originally Wesleyan, it passed to the Catholic Church in 1927. Destroyed or damaged in the war, a new church (the present one) was built in 1962, and it is indeed a chapel-of-ease to Westminster Catholic Cathedral.

St. Clement Danes, an unusual night-time scene. Another view. Both from an old postcards in Steve Bulman's Collection. A modern view, © Chris Emms (2009).

St. James, Piccadilly. © Bill McKenzie. Another view, © John Balaam (2011).

St. John, Smith Square. © Gerard Charmley. Link1. Link2.

St. John of Rila (Bulgarian Orthodox) on Jays Mews and Bremner Road. The only Bulgarian Orthodox church in the UK. TQ 265 795. © Martin Richter (2012). Link.

St. Margaret. © Bill McKenzie. A view from 1915, from Colin Waters' Collection. Interior view, © Peter Morgan (2015).

St. Martins-in-the Fields, St. Martins Lane. TQ 3008 8054. © Bill McKenzie. An old illustration dating from 1916, showing the church's setting in Trafalgar Square. From Colin Waters' Collection. Another view, © Roger Hopkins. Interior view, © Dave Westrap. Link1. Link2. Grade I listed  - link.

St. Mary-le-Strand. © Bill McKenzie. An old postcard view, from Steve Bulman's Collection. The church in the background is St. Clement Dane. Another view. © Chris Emms (2009). Link.

St. Paul, Knightsbridge. © Bill Henderson.

St. Stephen on Rochester Row. TQ 295 790. © Chris Kippin (2019). List. Grade II* listed.

Salvation Army Citadel, on Rochester Row. © Rob Brettle.

Westminster Abbey (the Collegiate Church of St. Peter). TQ 3008 7949. © Bill McKenzie. An old postcard, franked 1906, in Steve Bulman's Collection. Another view, © Aidan McRae Thomson. The Chapter House, north cloister, south nave and north cloister, Henry VII's Chapel, and statuary in the Henry VII Chapel, all © Christopher Skottowe (1963 and 1964), and from his collection of earlier photo's, another view of the Henry VII Chapel in 1938, and an interesting photo showing the Abbey with spectator stands, at the time of the coronation of George VI in 1937. Link. Grade I listed.

Westminster Baptist Church on Horseferry Road. TQ 2980 7901. © Chris Kippin (2018). Link.

Westminster Catholic Cathedral, or more correctly, the Metropolitan Cathedral of the Most Precious Blood, on Francis Street, was consecrated in 1903. From a postcard franked 1907. Collection of Mrs. Marion Allen. Another old postcard view, this one from Christopher Skottowe's Collection, and another (posted in 1934), from Paul E. Barnett's Collection. Two modern views - 1, 2, both © Gerard Doherty (2013). Link.