ok car in at dealers. they had a look and "think" the water pump has failed. i no this is fairly common but if my impeller had broken off would it not pump water around the engine?! making water not circulate and make it overheat?! certainly did on my old car! overheated within 10 minutes.. so why have i been able to drive my car to birmingham nec and edition 38 and many places this year without it overheating? is it magic or just pure luck?! im confused.com but there the guys who are in the no so hey let them get on with it.
new cambelt, water and thermostat.... price... but hey if its fixed so what!!! get it back 2morrow!
if the water pump failed, you'd certainly expect to see it reflected in the coolant temp, eg if the water isn't being pumped round, only the water in the engine is going to get hot, or the temp goes through the roof.
changing the water pump is a very drastic guess IMO on their part, as you've said its a common fault, but a very expensive test if it doesn't solve the problem (expect them to quote you £400-£600 for the pump / cam belt)
my first guess would be either a problem with the climatronic unit, eg the thermostat on that that regulates the temperature