[Laird Scooby]

Your battery isn't charging, the alternator is knackered. It should e 14.4V on a cold regulator dropping to 14.0V on a warm one.

Somewhere you're losing a bit of voltage and that suggests to me that the rectifier in the alternator is FUBAR. Common problem on those Bosch alternators, it loses one or both diodes on one phase, dropping the output by about 1/3 and also introducing a parasitic drain.

If you put the headlamps, HRW and heater fan on doe the charge warning light glow dimly, getting slightly brighter as the engine speed rises?

Also what sort of battery is it? As in, is it one of the new, "Calcium Technology", "Silver Calcium" or similar batteries? If so, your alternator won't charge it properly. They need a higher charging voltage of a minimum of 14.7V to 15.1V so if that's what sort of battery you've got, it could be what killed your alternator.