[Little Ray]

There are multiple Imperial War Museum sites. There are three in London - the War Museum at Lambeth Rd., the Churchill War Rooms, and the HMS Belfast.
At Duxford there is both the Aircraft Museum and the Land Warfare Museum. IIRC, you can (for a fee...) even drive tanks at the Land Warfare Musuem.
The Duxford air museum tries to restore their aircraft to flying condition - unlike the Smithsonian. It is probably the only place you can see a flying Hurricane, and they have a De Havilland Dragon Rapide that you can purchase a flight on.
Outside of the IWM complexes is the Royal Armoury museum. It has been moved out of the Tower to a museum at Leeds.
One very sad thing I encountered there was a nasty strain of PC. For curators of weapons museums, they are rather anti-gun.

[T-Bone Texan]

I went to one of the war museums in London - the one with the enormous naval guns in front.

There was a virulent strain of political correctness running through the place. I wore my USCGC Munro cap and got odd hostility from a visitor and an employee, I guess because folks thought I was in the military.

It was several years ago but I remember how out of place that behavior was. It’s a war museum for goodness sake.