Apart from the rear brake switch sticking on, caused by the connecting spring snagging on the brake torque arm bolt

This got progressively worse on the way home and Skruffy Kat valiantly made it back onto the drive, where she promptly gave up!
Knowing the history of 80’s GSX electrics and that the alternator and the reg/rec are original Suzuki items, I bit the bullet and ordered a new one of each from ElectrexWorld plus a new gasket for the genny cover and some other bits and pieces to do a service!