I saw this place listed on the page that the high speed train web site has, for free things to go do in London.
https://www.southeasternrailway.co.uk/destinations-and-offers/offers/free-things-to-do-on-our-network
Has Harry Potter art and more, by the original graphic artists, it seems.
https://store.minalima.com/about-us/
Has anyone been there? Reviews? Worth the trip? :) Thanks!
-Alison