London's got a pretty solid group of fixed riders but it is predominantly made up of messengers (although salmon got his messenger wings for knowing a soho alley that I didn't, props). probably about 50 or so total and the community here is mad tight because everyone who rides goes to the same pub every friday so we all know (if not recognize) each other. And the Herne Hill velodrome is hopping compared to Kissena. When I was there last it was a super slow day with well over 50 people there.