The spare wheel hub, is exactly the same size as the wiper motor housing, so if you just pop the motor and shaft in there (not your ‘shaft’ obvs) then tapping the rotor out is easy peasy!
So that'd be MG Rover, Service Tool :ZXK455632/B then!
About right! It’s such a perfect fit with the lip of the gearbox it was almost as if it was designed that way! Sadly my motor was too far gone and the whole thing was a write off.. new one on order! Bloody things