I was in London for 2 weeks, working in an office. I saw quite a few
single-speeds (like a Ted Shred but w/ brakes). And tons of fixes!!
Most but not all among messengers. The vast majority of the fixes
were conversions from road bikes. Very few horizontal dropouts, but
quite good fix-riding style, if you know what I mean - ultra
smoothness.

One day I rented a bike from Wes at

http://www.londonbicycle.com/bikes.htm

which is the best place I've ever rented a bike from. They don't
have fixes, but Wes is planning to get a custom frame built in the
U.K.

The Bicycle Film Festival was there, and at Wes's rental place I met
up with a few folks who raced an alleycat - but I was so busy with
work I couldn't join in the festivities.

Next time I go, I'm taking my all-new-improved Popdan Koostum!!