Compare to the quote that I've got for my Alfa
By co-incidence, I've just arranged for the cambelt to be changed on my Alfa 147, at a local independent garage.
Now I'm cheating slightly here, because I'm in the trade and able to get parts & labour realatively cheaply (particularly the parts), but my quote is as follows.
To replace cambelt, water pump and coolant £160 labour (+ VAT)
Cambelt kit, £55 (+ VAT)
Water pump £30 (+ VAT)
So the £200 quote does appear to be a little on the cheap side. I suspect your garage might be planning to just replace the belt, using the existing tensioner and pulleys etc. Make sure a complete cambelt kit is fitted, not just the belt itself.
The water pump change on my car is precautionary really. At 68K miles, do I really think I'm likely to get another 36K out of it..? Maybe, maybe not, but what I do know is that if it fails soon, the engine will have to be dismantled a second time with another bill of several hundred quid...
Incidentally, I would have done the job myself. It looks perfectly feasible for a competent DIY mechanic, but the cost of the necessary tools is prohibitive. Particularly if you only expect to do the job once in your lifetime.
But if you really are an Alfa nut and plan to have this job done regularly, perhaps on several different cars, I reckon its worth the investment in the necessary tools...