Welcome to AO, NJH...enjoy your stay here and you should find this a very friendly place to visit.
Warnings about Alfa's quality and reliablity are rather extreme if you read newspapers and the motoring press (IMO). The quality has improved greatly with the recent Alfa models particularly the 156 and 147 and are closing in on Germany's best. If you read some of the threads on AO dont be too alarmed as obviously a lot of the posts are with particular problems being researched by people looking for information - most owners will say that they are very happy with owning an Alfa.
If you do want to know what to look out for here's a start.
Camshaft belt replacement - ignore the handbook recommendation of 72,000 miles and assume that it should be carried out at 36,000 miles for safety (other manufacturers are also erring on the safe side also).
Suspension bushes also are prone to premature wear but depending on the previous history for a used car these may already have been replaced.
If you are buying from a dealer look for a good warranty.
Servicing costs are generally higher than other car makers and only a main dealer or Alfa specialist should be used.
Alfa dealers are a mixed bag but generally come in for a fair amount of criticism. I have no experience of Perry's in your part of the country - perhaps another member has.......
The best thing right now would be to have a test drive (if youv'e not already done this) to see if owning and driving and Alfa is for you......