HELP! Currently in London, UK and looking for great places to find collectors items

[Lazarusxx]

Hey community!
I am currently in London, England and I'm looking to find some great places where I can pick up collectors editions, steelbooks and most things collectible.
Although I am on vacation I like to try to be a bit cheeky and sneak in a visit to a gaming store if I can get away with it. I have already visited a GAME location near Oxford Circus but they weren't helpful in the slightest so I'm turning to the community for help - something I should have done right away.
My base of operations is Earls Court so any help would be appreciated! My last day here is August 11 so if you can, please help!