Help :) fuel problem !!

[JG22-VXR]

Hi, first time on here, i have a problem regarding my fuel, i recently filled my petrol tank up to the top & since have noticed its leaking from the seem in the middle by the fuel filter, i know the obvious that i need a new fuel tank, but since i filled it i have done 200 miles and the fuel gauge is still reading full :S i would assume it may be the fuel sender unit, just wondering if anyone could help me out abit here?