I've had a number of Uno's and have seen two alternator types
(there may be more). Don't worry too much about the rating.
(unless you have a 500W hi-fi and sceneary scorching
headlamps)
The main things are the connections (type of plug) and the
adjustment. Some Uno's have a separate punched fanbelt
tension adjuster, others (I think later models) the tensioner
is part of the front casting, this extension making it harder
to get it out past the driveshaft.

Local breakers about 20-25 quid for alternator.
Local auto electrician  of the old school, with skimming lathe
for (starter) commutators, pullers, press etc, 12 quid to replace
the front bearing. Also good for sourcing the alternator
slip ring bushes, and starter brushes. Nobody seems
to fix starters and alternators any more.

I buy a breakers yard spare, then it's a simple swap to keep
you on the road, while you get the other one fixed.