Much depends on time of day and day of week as to the type of crowd that shows up. Yet you can go to the same one twice and have two completely different experiences. I tend to go like Chariots in Shoreditch for the sheer size. Sauna Bar is a smaller and nicely run place. If you just want to go to a a sex club, there is Vault 139 near Warren Street, and it's a really good value comparatively. Have fun and stay safe!