Aw you'll love it in Landaaaaan (those from London will get th "joke".. I hope lol)
Anyway, there's the West End Magic show at the Museum of Comedy on Bloomsbury Way in London. It runs between the 3rd and the 18th of December and there's showings at 2pm and 4pm. As others have mentioned, you have Davenports, check out Hamleys toy store too, they have a neat magic section on the 4th (maybe 3rd) floor. If you're able to make a detour, Bristol have a lot of magic related goods. Then you have my hometown, Birmingham, further up North where you have the Bristol Magic Society, located in Selly Oak. Hope you have an awesome time wherever you go