Erratic TD5 Fuel Gauge

Hi everyone

Over the last few days my fuel gauge has been showing the wrong reading sometimes and the correct reading others. What i mean by this is when I turn the ignition switch it either;

1. goes straight to the correct level and "behaves" as normal and goes down depending on distance
2. goes to the correct level then very slowly goes to empty in about 15 seconds
3. starts at empty and then very slowly goes to quarter full
4. starts at empty and then slowly goes to the correct level.

When it goes to the correct level it will read correctly and everything is fine. It has just started to do this. I know straight away if it doesnt read correct and just turn the ignition on and off until it goes straight o the correct level.
When I was driving yesterday it went from 3/4 full to quarter in about 30 miles and so when I filled her up it only needed a quarter of a tank.

I fitted a new fuel pump about 2 months ago, the correct size for this model, I also fitted a new tank ring. I cleaned the tank and all of the connects etc were inspected and were in good condition. When I replace the rear crossmember, I took the tank out so all the work was done on the bench, so a good environment.

I'm hoping someone is going to suggest its the dial, because when I finished the rear crossmember and reinstalled the tank, I ran her for about a month before I put the floor back in and then rovotted her and also Tiger sealed all around the edges. Oh and no I didnt cut an inspection panel in the floor. Any helpful suggestions appreciated

Cheers

Stumpy