In time for the weekend, if you are looking to attend church in London, Dr. Fumblefinger correctly identified the church in Puzzle #23 as Saint Helen's Bishopsgate in the City of London, the famed square-mile heart of Greater London. The building dates to the last years of the 12th century.
It's one of my favorite churches anywhere; I've gone to visit every time I've visited London. I first found it by accident, looking for a nearby shop. Turning into a passage lined with shops, I found myself facing the building and wandered in.
St. Helen's is tucked into a quiet corner, approached through a modern building that stands where the Bishop's Gate did once, and has an unlikely neighbor: Norman Foster's Swiss Re building, also known as "the gerkhin" or "the bullet building."
It also has a string of "specials:" It's both the oldest and largest church in The City; it has more memorials than any other church in Greater London except Westminster Abbey, and it was William Shakespeare's parish church when he lived in London. It survived both the Great Fire of 1666 and the WW II Blitz, but was heavily damaged by IRA bombs in the early 90s that destroyed a building next door.
That damage led to a major change: the architect for the repair of the church returned it to its 17th-century Restoration era appearance, stripping away a lot of later additions. As a result, the church is marked by white walls, strong woodwork and a great deal of light. One of its most unusual features is its two-nave design. One was originally for an order of nuns founded in 1210 and the other for the parish; a curtain the length of the church divided them.
Saint Helen's also has a magnificent organ, visible in the pictures here. It was originally built in 1744, and rebuilt in 1810, 1910, 1923, 1929, 1957 and 1996. It has to be one of the most restored organs ever!
As Jonathan L. and Dr. Fumblefinger noted, there are no pews. Saint Helens (whose name, due to parish consolidations is now actually "St. Helen Bishopsgate with St Andrew Undershaft and St Ethelburga Bishopsgate and St Martin Outwich and St Mary Axe") has an active congregation with many local events, classes and activities; the room is set up as needed for meetings, services and more.