1998 Ford Puma fuel guage issue

 HI.. i recently bought a Ford Puma 1.7 1998 and had no problems till last week when for some unknown reason my petrol gauge a started acting up.
It now appears to be stuck on full when i know for a fact that it only has about 1/2 tank left.
This is proving to be a nitemare as when i go to try and put more fuel in it wont allow it as believes its full.
If anyone can help that would be amazing as i need my car desperately for work, as live 50 miles away from work and work for the Emergency Services.
 

beaverlock; The Petrol guage has absolutely nothing to do with allowing or disallowing petrol into the tank. The guage just 'tells' you how much is in it. Two, seperate, problems I'm sure. Have you owned this long enough to go through several tanks of petrol? A plugged or pinched petrol vent hose can inhibit filling the tank as it won't let air escape quickly enough as petrol goes in. The fuel guage issue is, more than likely, the sending unit in the tank which is, again, usually part of the petrol pump assembly. You'll have to check with Ford on that one. It is possible that the previous owner, if you haven't had it long, could have tried to replace the petrol pump and damaged the sending unit and pinched the vent hose at the same time, but this is just a wild guess.