Thank you, both for the welcome and the advice! I am in west London (not far from Westway, and I've got a taster session there tomorrow to hopefully remind myself how much fun it is!) but the only friend I know who climbs regularly does so at the Arch (which is apparently closing according to its website? And also seems to be mainly bouldering as far as I can tell?). I would like to try route climbing as well as bouldering, so maybe I'll stick to Westway for now.