Have you asked for a signal booster from O2? We're in a poor reception area, too. After I complained about it, they sent us a booster box. It's tiny and makes such a difference. I can actually make calls on my mobile now as well as send/receive messages etc!
Unfortunately I renewed my contract with 02 just before they stopped Tugo. If I had known this I would have had serious second thoughts. We don’t get a consistent signal here at home so I was able to access my mobile from my iPad. As so many people use their mobiles now I can see this costing me dearly when I return the calls on my landline. Has anyone else been affected and, if so, have you come up with a solution?