In reply to Flying Monkey:
I find that the three major London climbing walls have a distinct groove each.
Mile End - students and "working class", grimey, friendly and hard routes
Castle - trendy, a bit yuppie, rammed full in the evenings, expensive, few difficult lead routes
Westway - sport-center/family groove (floodlit, tennis center), focus on lead climbing, lots of kids and classes.
This is the impression I get, anyway, but I have to say that I have been to Westway and Castle only 5-6 times each.
Anyone else feel similar?