The Lego Store in London's Leicester Square. The entrance is based on a train station design, complete with large Lego train you can sit in, a Lego London tube map on the wall, and Lego London landmarks. Over two floors, there is plenty of Lego of all types which would keep fans occupied. However, even if not a fan, pop in when passing and see it.
Transport & Parking
It's in central London so driving and parking could be difficult. There is lots of public transport nearby; buses, taxis, underground (Leicester Square is closest) but depends on your individual needs which is most suitable.
There is flat access from the street into the shop. The doors were open and a member of staff welcoming as you arrive. There are stairs between the two floors but also a lift.
I'm not aware of there being any toilets
I didn't require assistance from staff, but they seemed approachable