Had a look at your post since you replied to my thread
Same issues as me,

Fuel light
Low washer level
Fuel guage
Coolant
RPM
Batt
Door/light warning panel etc, are all powered off of fuse 22 (10 AMP)

I lifted up my fusebox and found the following, everything above is powered by a black and yellow wire that goes to fuse 22 and also connects into the BIG tall yellow relay in the fuse box. The other side of the fuse (closest to the front of the car connects to fuse 21, whcih I am led to believe does the other stuff that doesn't work-oil/handbrake etc, thats my project to look at that when i get home from work).

If you have a voltmeter or can even borrow one, take out the fuse and measure the voltage accross where the fuse would plug in. I did this before and it was 12v so it threw me, but turned out the contact underneath were fucked so i loooked elsewhere for a while only to find out that the fusebox was the issue.
Do this and see what you get, or better still, open the bonnet and "wiggle" the fuse when the ignition is on and you should see it light up if there is a bad connection.

Don't try and look under the dash as there are about 10 black and yellow wires and you won't know which one is which without tracing them, i did that and it took friggin' ages!