Triumph 2000 in Manchester:
Hillman Imp in the National Museum of Scotland in Edinburgh:
Reliant Robin (and a friend's TDI-equipped Defender 110 in the background)
Very popular cars since according to British law, a vehicle with three wheels is classified a motorcycle provided its engine doesn't exceed a certain size (determined by cubic centimeters). That meant these three wheeled Reliants were cheap to register. Safety concerns killed them.
Obviously not British but interesting nonetheless. Rarely seen here in France, they're around in the UK because Brits share a certain affinity for station wagons.