Gay tours of the U.K.
LGBT tours of Great Britain
Though there are tours for gays and lesbians in Britain, most gay tour operators run trips to destinations that are, well, somehwat more exotic than the United Kingdom.
However, you will sometimes find gay tours in Great Britain, along with specially sceduled gay transatlantic Queen Mary cruises (which has to be one of the first completely natural quadruple-entendres I've ever encountered).
If nothing else, the specialist gay tour operators listed below may be able to help arrange a bespoke gay tour for you, even if they have few group tours on their schedule.