Thanks for all of the replies, answers to specific questions below:

1) yes the charge light lights-up to full brightness at start-up, it then drops to barely visibly (rather than extinguishing) and remains there

2) how long has it been happening - I got the car back from the mechanic on Thursday 14th August, this was when the starter motor was replaced. I noticed the light about 2 days later, but it could have been there since I picked it up, it’s so dim I didn’t notice it until I moved the car at night. During the day I you really have to look to notice it. So less than 2 weeks.

3) no I didn’t buy the car this way, I’ve had the car since 2019 and the light has never come on before.

4) build date appears to be October 2003

5) when I wrote “voltage appears to be consistent” what I should have explained is that the mechanic measured charge rate and got a consistent 14v but didn’t measure from the alternator, as per suggestion. I will ask the mechanic to measure this and will also get a plug-in voltage monitor, that’s a great suggestion, thanks for all of the help!