Re: Newbie saying hello
The cambelt should be changed every three years or 36k miles whatever comes first. After that you are on borrowed time. The service manual probably still reads every five years or 72k miles, but the chance that the cambelt / tensioners will last that long is extremely unlikely.
There are lots of Alfa owners who needed a complete engine rebuilt because of a snapping belt before 5 years / 72k miles. Go to an Alfa specialist to do the job. Can't say how much the costs are as I don't live in the UK, but it should be doable for around GBP 400 (includes regular service)