a couple who wants to start swinging. will be in London in Sep

We are a couple from Sweden, who will  visit a London in September. We have talked a lot, and think we would like to visit a swinger club. We have googled some but many are a little outside London, (which is ok :) ) but they usually start rather late.
Is there any club which is within easy access from London and doesnt  open too late, and is good for beginners? Or are there other places? We
looked at Rio's but it seems a little unerotic :)
Thanks!