Hi Brett,
The science museum is quite good You can see animations of some of the engines in the museum here:
Copy and paste the link. If you can get to the midlands the Black Country museum in Dudley is worth a visit, it has the oldest rotative steam engine in existence, and it is still working. There are many other steam and engine museums in London (and elsewhere in the UK) which are worth a visit.
Myhobbystore though is just an online shop I think. It does not have physical shops, but I may be wrong! Someone will confirm that. I don’t know of any shops that sell models, castings, tools etc in London but there are a few such as Reeves in the Midlands (check Reeves 2000 on the internet.) and I am sure there are others around, perhaps other posters can help. use this link to visit Reeves:
Enjoy your visit
Terry