Can I recommend going to your nearbyu O2 store if you have one - the manager, if they're friendly, should be able to show you the masts in your area - they have access to a superior form of mapping than the public web coverage system O2 provides. You can then see if there are planned masts in the area, and they are likely to know the way to get a request in for one (and also show you how to game the system by getting fellow O2 users to make a recommendation to get a 3G mast put in). It might be by density of population/number of O2 customers in area, simple thresholds (like broadband actiavtion/LLU (think along the lines of samknows.com a while back).