Talking BARVs, the last M3 Medium in service anywhere was probably a BARV version with the Royal Australian Armoured Corps, used (for training) until 1972.
Talking Centurions and WW2, yes, some made it to troop trials, but then again would anyone argue that troop trials constitutes service?
Seeing how the Brits were just able to get some - not a huge number - of Comets into service, and kept Comets in service until 1962 in Berlin and Hong Kong in ‘trip wire’ units, that is just good enough to have to be knocked out, but also good enough so that if they are knocked out it means the enemy is serious; the Comet was really the ultimate Brit tank of WW2.
If they had really wanted to expend the energy and effort they could have gotten Black Princes into combat in Europe, and these would have been useful for the slogging through Japanese home island defences if armed with a 94mm howitzer rather than the 17pdr.