it doesn’t work properly when in the country side
What do you mean? Was it failing to find your position, or just not loading up any maps because it couldn’t get a data connection?
Being in the countryside shouldn’t make any odds to finding your GPS position.
So if it is the latter and you were planning to use it for navigation then check out one of the apps with pre-loaded maps.
MotionX GPS is cheap (69p) and lets you pre-load large areas of OpenStreetMap/OpenCycleMap (for free) and navigate via waypoints. It can also display your position in OSGB, rather than lat/long, which is handy when comparing to a paper map.
Viewranger lets you pre-load Ordnance Survey maps (as flyingmm says) – but they cost money.