Yes you still have to join before playing. Its down to 24 hours and that can usually be done over the internet or fax before you get to the club.

Each club is still independent of the process so that even though Grosvernors has many casinos in and around London you will have to join each one (however their computers are linked and they can electronically forward your information to another casino so its very easy to join a second Grosvernors).