I personally think that Alfa has three problems in the UK, dealers, dealers and - er - dealers !
Alright,I'm biased as a I love Italian cars in general & Alfas in particular, but I don't think that the cars themselves are necessarily more unreliable than any others.
I, sadly, have colleagues with BMWs & Audis which have no end of problems, and my brother had an Audi TT which was an utter disgrace, but the difference is that the Dealers actually made efforts to help their customers, sorting problems out, actually being open at times when you could pick up & drop off cars and of course providing courtesy cars.
Most Alfa dealers, in my experience, find the whole concept of courtesy alien, let alone providing a customer with a car !!!!
My, brand new (at the time), local, flagship, GTA dealer was in my first year of dealing with them a complete disaster( although to be fair they have improved recently), but most non alfisti would have just walked away in that first year.
What does concern me though is that a lot of this must be the fault of Fiat UK, once again my local dealer also has a Nissan franchise which is regarded ( apparently ) as superb, so I assume that it must be more to do with the supervision of the dealers than the dealers themselves - as I assume the Fiat/Alfa franchise must share some management with the Nissan one.