Hi Tim, and welcome to AO.
You are correct, you should aim to get the cambelts done as soon as possible. Although the original advice was to have them done on 72,000 miles, Alfa Romeo have since lowered this, to 36,000 I think.
The variator is a little gizmo that adjusts the timing between low and high revs, it's a slightly primitive alternative to Honda's VTEC system. They aren't expensive to buy, but to fit them requires the same work as the cambelt removal, and they have a similar life-span to the belts, so it makes sense to change the variator at the same time.
I think it'll probably add about £50 to your bill.
From my experience, and the other people on here who have posted about a variator problem, when it goes, it tends to stick at the settings for high revs. This means that the car can sound a bit rough, almost diesel-like, at idle, and can be a bit sluggish at low revs.
Anyway, to cut through the waffle:
Should you change your cambelts? Yes
What about the variator? Yes
Oh, and your MPG is on the lower side of normal, but it is normal, sorry. Not a chance in heel that you'd ever get 40mpg.
I have the 2.0 Tspark in my 145, and I get about 31mpg, which everyone else on here with the same car thinks is very good.
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