Well after thinking that I had seized/stuffed Alternator bearings, the weather cleared today and I had a delve under the bonnet to discover that the Alternator was in fact fine, but the Aircon pump was seized solid. Haven't yet worked out why its solid as the drive to it is via a magnetic coupling, but seized solid it is.
So, it looked like the easy fix was to bypass the pump and the idler wheel, and use a shorter drive belt running just the crank, tensioner, and Alternator. Shorter belt now ordered, and hopefully ready for collection tomorrow, fingers crossed.
At the same time as the belt issue above happened, the offside Headlight unit also completely stopped working. A quick look in the fuse box next to the battery didn't seem to have any fuses or relays for the lights ?, so there must be a secondary fuse box hidden somewhere ? (answers gratefully received).
Hopefully the old girl isn't dead yet, but certainly under very critical assessment.