In reply to FrankBooth: As said above, if the loss of weight is from the rims then the bike will accelerate more easily (less of an issue with flat or rolling steady paced efforts, hence why TT bikes have wheels more focussed on aerodynamics than rotating mass).
You'll also be limited in how much lower you can go with the bike weight - at £1500 you can probably get a sub 9kg bike and the UCI minimum weight limit is 6.8kg, so unless you intend to take a drill to it as some domestic climbers do, you won't lose a huge amount.