Thanks for the reply mate. Started it this morning. Same noise (as was cold). Shut it down and whipped off the auxiliary belt. Started it up and completely quiet... (so hopefully....) - phew!

I spun the alternator by hand. Smooth and silent.

Power steering pulley has a knock on it:

https://youtu.be/CeuNubMAXFQ

What do you reckon?

As soon as I put it all back together the car was silent again.... not sure if spinning the power steering pump in reverse (as I span it back and forth) may have lubricated it differently to normal - but am starting to think that it’s the culprit as you suggested...

Thanks again for input - been on forums for years now and appreciate the advice (and try to help others back too!). And also - very kind offer re the pump - but yep. Probably not the most efficient route to repair!