When I called to arrange I said that I wanted the water pump changing and the dealer talked me out of it. His very words were that "if this was a Mk IV Golf then I'd reccomend it but we've had no trouble with the Mk V's and with your mileage I can't see the point in you doing it".
So, no I'm not having the water pump changed and although I hear what everyone has said if my dealer is telling me not to spend then I'm taking his word for it.
Simon