Wonder what sort of expense is involved in replacing my cam belt and water pump?

I would say about £130-150 is a fair price independent , if you can get it done at Fiat for a touch extra I would do that. You may be able to find cheaper but i dont think thats the norm

From experience with my previous panda I got a good independent to do it and the waterpump quality they used was rubbish and they used blue regular coolant when yours needs read OAT which is x2 the price. My head gasket went under 6 months later and im quite sure it was something to do with it.

If you buy the kit yourself, be real careful because it goes down to engine number & wherever you go specify RED OAT coolant.