XR5 fuel gauge issues - help please

[peachey80]

Hi all,
I've got some issues with the xr5, fuel guage is playing up, won't show full after filling and doesn't go down much. Missus put 50L in it the other day when the gauge was reading over half.
Is this a common problem? I've read on issues with the other zetecs, but not the xr's.
I'm guessing a new sender unit ?
Anyone had this ??

Thanks in advance.