Thanks for your help Corcai but i'm struggling. My support bracket is slightly different to the one in the photo. Yes it has the 4 bolts as in the picture but the casting on mine also incorporates the alternator and the belt tensioner. Anyway, I've taken the alternator off its mounting but can't get it out of the bay so fiddled and finally I've loosened the 4 bolts. Nothing, still solidly attached to the engine. Do I have to now split the driveshaft from the wheel to allow me to move the support bracket or is there something else I'm missing.
Wish I'd never started.