The wife has had a 147 2.0 t-spark for a few months now, and after much searching i found an independent who replaced the cam belt (and other associated parts) for £300. He was by far the cheapest and did a great job. He was back again today to do a service, which again was very reasonably priced.
More details can be found at
A For Alfa
We're in the Berkshire area, and he came out to do the work. I'd recommend him highly.