Thanks all -
I've managed to obtain a different FF7 off a mate, and using that save game I've been able to carry on, up until the first visit with bugenhagen, upon which it crashes.
I guess I'll have to just leave it - too many crash points, far too annoying, plus I have to admit I find the action too bland in comparison to FF8, so I'm going to abandon FF7.
Thanks all for your help, nonetheless.