If you do end up needing to change the water pump, change the cam-belt, tensioner and pulley too.
The parts will cost just something like £70 from www.shop4parts.co.uk
etc. and the old ones have to come off to remove the water pump.
You may as well put it back with all new parts... Cam-belt/tensioner are supposed to be changed every 36,000 miles or 3yrs... so this will sort that job out, if yours is due any time soon.
You may want to also consider the cam-variator.. if yours sounds remotely dieselly on start-up... but they're £100... so it may be worth a punt on keeping the one you have, if it's dead quiet at the moment.
Meanwhile.. I wouldn't do any long trips if your water pump is the culprit, since if the bearings collapse, it will make the cam-belt go slack and that will wreck your engine.
I don't want to alarm you..
but it'd be a shame to take too much of a chance, having realised that it may have a problem and be about to fix it..
Shop around for a specialist that can fit a cam-belt (water pump is an extra 5 minutes on top of that job). www.AlfaWorkshop.co.uk
etc.. can do the whole cam- and balance belt doodah for £300 which includes all the parts you need... (You'll obviously need to add the extra cost of the water pump).