Fuel gauge reading wrong

May be the sender in the tank that is faulty, many modern scanners of good quality can tests this circuit, but i would suggest that a dealer do the inspection as their equipment id designed pacifically for your car and you will get a correct diagnosis first time.

Thank you. I hope it's nothing to serious

so do i.... please up date any progress here as it may help others and if you get stuck we are here to help as best we can.