I too had a problem with the Ford Focus cluster problem, fuel gauge showing full when I knew it was around 1/4 full.
Read various posts including Watchdog (tv prog), which gave details of spraying WD40 or similar on the rear of the PCB. I have now done this and the gauge looks to be working, need to keep an eye on the level to see what happens, also have a gallon of fuel in the boot should it be reading wrong and run out on me.
It's very easy to take the cluster out and put back in, I have taken pics of each stage if anyone needs them just e-mail me.
[email protected]
Stu