How can I fix my old style Jaguar XKR sat nav?

4 year old car though last of the old style. Sat nav never really worked but didnt bother me as i am a complete technophobe and still used a map! Now that i have tried to use it its busted and no longer in the warrenty period...I can already hear your violins. Anyway took it back to Jags who told me it was the antenna but it was a 7hour job at £120 pounds per hour plus cost of antenna plus VAT...i got out the old map book again. Infact i decided to take a look and found that changing the antenna was a 30 second job...cheers Jag, found a dealer that had an antenna in stock so drove 50 miles to try before i buy and the damn thing still didnt work...got lost on the way back home. The problem with the sat nav is that everything is working ie screen,maps, voice etc but the car doesnt recognise where it is as it appears not to be picking up a sattelite signal. Therefore i have had many interesting journeys supposedly across fields and even vast expanses of water...suppose i should sign this off James Bond