Yes, you can just turn up. It's being advertised on TV at the moment that registration is free, but you have a weekly fee still to pay, but I don't know how much it is, sorry. I imagine it's probably around �5.
Just a query to go with your link re Implanon which may tie in with this question - have you put weight on because I have put over 2 stone on since being on it? Wonder if it's a major problem