Regent Hall, W1C 2DJ
On Oxford Street, this is actually a Salvation Army church, but it has a cafe.
[Susannah]? went there just because it looked cheap, and was pleasantly surprised. I had a quiche with salad and a cup of tea, and got change from £3. The quiche was hot (not tepid), and appeared home-made, and the salad was fresh, plentiful and varied. They also did Fairtrade snacks and other light lunches.
Staff were efficient and friendly, and the seating area was comfortable, if a little small.
I didn't notice any obvious evangelism, but it is possible that this might be an issue for some people.