As someone who lives in rural Lincolnshire I can tell you that it is a combination of phone and network. The signal occasionally drops out completely. I've had four bars in the Living Room and No Signsl in the kitchen 20 seconds later. I have also had no signal when my wife has had nearly a full signal when we are in the same room but with different phones.
Firstly may I point out that O2's 3g signal in Lincolnshire is non existant outside the major towns (Grimsby, Lincoln, Scunthorpe, Boston, Skegness) except for a very small area in Ingoldmells and Humberside Airport. The 2g signal is non existant for parts of the coast (espcially between Mablethorpe and Cleethorpes) and for large parts of the Wolds. When the area first got mobile phones everyone had a Nokia and O2 had the strongest signal. My wife has stayed loyal to Nokia and O2 and has had very few problems with coverage, myself and the children have moved onto other phones (LG, Sony Ericsson etc.) and have had far more problems.
Finally I have to add that other companies have overtaken O2 when it comes to signal. You can get areasonably good 3g signal around most of the county with both Orange and T-Mobile and Vodafone isn't too bad.
My only advice would be to maybe get a Nokia just for your trips to Lincs. The only other option is semaphore.
