The water pump is an optional change, depending if your one is worn.
But quite often you can't tell if the waterpump is worn. How on earth can you say something like that?
I'd replace the waterpump as well (it's only £30, and there should be no additional labour in replacing it). You can also get the coolant changed at the same time (this should be changed every 2/3 years anyway). You need the cambelt off any way to change the pump, and at this age and mileage now is the time to do it.
The trick with Alfas is to minimise the risk. Cut corners and, sure enough, sometime down the line you'll pay.
Of course the so-called specialists will be very happy to see the waterpump go, either necessitating a cambelt off job to replace, or an expensive engine rebuild (it has been known for these pumps, however durable there reputation may be, to strip the cambelt when they seize).
Just do a search on here on this topic and you'll soon get the drift.