I recently got the Cambelt, Balancer belt and Tensioners done at Gonnella Brothers in Catford for 220+Vat.
The number is 0181 690 0060, 9/13 Catford Hill.
I spoke to Adrian (AlfaAid) about this, he said he couldn't even get the bits for that price. He also said that Gonnella have been around for donkeys and are OK.
I saw an ad in Autoitalia recently which detailed prices for genuine 155 service parts, including the belts: can't remember the prices but it was cheap! Might be worth getting hold of an issue?