Re: end UK dependance on GPS?
I'm quite sure I have previously read about ship navigation beacons similar to how a lighthouse works. The beacon ( lighthouse would be a good place to situate it) sends a very accurate time signal along with a location ID, some clever maths and a lookup to the location database would be able to give a very accurate distance from the known location of the beacon. If you have 2 or more beacons in range you can calculate your position, the more beacons in range more accurate you can be. Virtually the same as GPS and other space based versions but obviously needs more beacons due to the curvature of the earth etc (if its flat.. I'm not going there).
Anyway the ground based version should be massively cheaper for local navigation / busy shipping lanes where line of sight is not such an issue.
I think the main problem would be putting up these beacons in enemy territory so bombs could be dropped where you intend.... And that's why GPS etc can be turned off and has encrypted channels, just in case you know.. Oceana are allies with Eastasia today...