I have the same problem, wondering whether it is a poor connection to the
fuel pump, have just sorted out how to remove the back seat now find a
rivetted plastic cover, watch my posting, we might both learn something

I have the same problem and am doing the same every 500 miles filling right
to brim.  With my air con problem, passenger window doesnt work, and
this..... methings time to sell..................

When the car was in the dealers they asked whether I filled the car
with the key turned on in the ignition. I did not think so but cannot
be sure as I was 2/3rds the way through a 960 mile journey non stop to
the French Alps (canoeing).

Today I filled the car to the brim with the ignition  turned on, lo
and behold the gauge stuck again then after a while moved to full.
What I need now is the nerve to not fill it until the gauge shows
empty or it runs out. I am going to on hols with my caravan which
should take 3/4 of a tank . I have a can of diesel in the boot and
will try and run it very low but the consumtion varies a lot towing
and I do not want to stop somewhere dangerous.

Will report back in 2 weeks

Frank B

Now back from hols.

Kept my nerve and ran the tank very low, the guage is now working
properly. The problem must be caused when you re fuel  withiut turning
off the ignotion properly. £600 saved.

Frank B