Alternator problems, smoke coming from pulley end of alternator and battery light on so I suppose it's done for. Couple of questions.
1) any possibility it can be repaired eg new brushes (does it have any?)
2) looking on eBay there seems to be more than one make of alternator available for this car, is it important to have one from the same manufacturer.
3) a few weeks ago I changed the timing belt which involved taking off the alternator belt. Is it likely that I may have then over tensioned the alternator belt, causing load on the alternator bearings, causing heat generation, causing burnout?

Not worth messing about with. Remove it and get a reconditioned one, here in Spain no trade-in is necessary, don't know about UK.

Scrapyard replacements can be almost as bad as your own, unless the car was driven in and immediately checked over by somebody who knows what to look for.

first get voltmeter and measure voltage on battery when car is turned on, mk2 punto alternator will fit mk1 too, what engine you got?

it is possible you over tensioned the belt yes. did you spin the alternator to check it span freely when changing the belt?

you probably can get the parts to rebuild yourself if you search and make some calls, not something i have ever bothered with though.

I would buy one already reconditioned or find somewhere local that reconditions them. If you just buy one you want to make sure the pulley is the same as yours, some later puntos have different spacing for the pulley so it won't line up with the crank pulley even though the alternator itself is the same (could just swap pulley over from yours though if that happens). Which one you get doesn't matter hugely so long as it is rated to deliver as many amps as the one on your car - i.e if yours says 65A on it don't fit a 55A one but a 70A will be fine

I once spent time and money to remove, strip, replace brushes brush holder and regulator, cleanup and regrease, put back together and refit to the car, only to have it fail a month later when the brush tracks finally wore right through the copper onto the white insulation below which was not apparent first time. Then I went out and bought a nice new one from Femsa, with a guarantee. At least I knew how to go about iut second time around!

Don't waste your time with high-mielage electrical parts.

Hi,
Almost certainly bearing failure. May have been worn for a while and tight new belt finished it off. As it may have caused other damage I'd just put a reconditioned one on. Unless you have bearing pullers and a press DIY is a bit of a faf and not worth it unless you want the learning exercise.

Robert G8RPI.