The first British built tank with a name as part of the official designation was Covenanter. It was a cruiser tank and it started the trend.
Infantry tanks were named differently, Matilda and Valentine. Churchill was, presumably named after the man himself.
The cruiser line ran, Covenanter, Crusader, Cavalier, Centaur, Cromwell, Challenger, Comet, Centurion, Chieftain and Challenger.
They also mostly had alpha-numeric designations. Covenanter was A13 Mk111, Crusader A15 etc.