Not sure if this is in the right forum, but people have asked in the past about London-based writing groups, and here's one:

'The Camden Town Writers' Circle is a new group which meets every other week over drinks to offer support and feedback on members' writing. If you're looking for candid but tactful feedback on your material, come along - we're a very down-to-earth bunch and new members are welcome. So whether you're working on a novel, screenplay, sitcom or children's book, if you're serious about getting published, we're the group for you! For more details, please contact: londongirl111@gmail.com'