Okay, here's the story:
The battery warning light has come on and stayed on for a couple of days. The alternator bearings have been abit whiney for a couple of months but it has, until now, kept the warning light off and the car has not laboured whilst starting so I've left well enough alone. The thing is that despite the warning light being on it is still starting fine and when running there is 14.5 volts-ish across the terminals. Surely if the alternator was supplying insufficient charge then there wouldn't be this kind of voltage across the terminals. Could this be a dicey battery. I have been quoted £75 for the alternator (apparently there are a number of different ones possible for Cinqs and mine is the most expensive, identified by it having a grooved belt rather than a 'v' one). Is there anything I can check before renewing the alternator?

remove the alternator and take it to an autoelectricians, the one near me will test them for free

Tried the local autoelectricians. Couldn't have been less interested. They only seem to be interested in ICE installs.

I can't understand why, if it's jigged, it's putting a decent voltage across the battery, and the battery is maintaining a decent charge.

what does the battery put out on it's own? should be around 12.4 volts if it's healthy. then start the engine and switch straight off. if the battery has registered a drop of more than .2 volts then assume it's shot. batteries for cinq's are expensive though, ours just cost 50 quid!

Jon+Em