when you flick threw the dash board display thingy. it normally tells you how many miles you have left in your tank, normally when mines full it goes to around about 350 give or take well today when i started the car, the dash was slow at starting up and when it did my fuel gauge started playing up saying i had more in than i did and my dash board thing said i had 420 miles left. ive tried disconecting the battery but it stayed the same so i went and filled my tank to see if that would help but now although my fuel gauge says full apparently i have 500 miles in my tank. can anyone help me please???????

Sounds like you have a fault in the fuel level sender circuit.
Best to get a mechanic to diagnose.

Are you really only getting 350 to a tank? I normally get 450.

yeah thats all it normally goes up to. but now its gone up to 450 +