There are a number of Gluten Free bottled beers readily available in the UK. Most supermarkets stock them, however the stocking of Gluten Free beers in pubs and bars is a bit more hit-and-miss.
I have not seen any Gluten Free draught ales anywhere yet.
Last year there was a newspaper article on the subject that you might find useful:
In pubs or shops? For shops, there is a gluten-free Tennents lager (Gluten Free T), Celia Czech lager, Brewdog Vagabond and Daura Damm. All available in Tesco and probably Morrisons and possibly other stores. Other choices may also be available like a gluten-free Old Spckeled Hen, if you like a darker beer, but I can't recall actually seeing it.
I spotted gluten-free Peroni in a supermarket the other week. Haven't seen it in a pub or restaurant yet though.Edited: 06 August 2018, 19:07