To keep the costs down why dont you do the service and cambelt yourself, as i am sure the punto owners on this forum would help give you a guide to doing it. the cam belt and tensioner can be bought for about £15, and a service at a garage will probably only do the air filter, oil change, and spark plugs (which you could easily do for £25 max). With regards to the clutch price, try ringing a few different garages.