Hi,
I have done a search and it appears that the fuel gauges do play up from time to time but my issue seems a little different.
My gauge keeps jumping from empty to full and then back to empty again every mile or so.
When it is showing full it shows my range as 537 miles and when it is showing empty the range shows three dashes.
I am confident that there is almost a full tank in there.
I have done a battery reset but to no avail.
Has anyone had similar issues or any idea what is going on?
I have a long trip to Scotland next week and could do without further expense!

Schroedinger's fuel tank?

On a serious note it sounds more like a sender or a level valve on the fritz.

Worth checking the connections under the rear seat?

Good luck.

EDIT:

http://www.fullfatrr.com/forum/topic21319.html This sounds similar