2.5 diesel gauges going doolaly

[micktheshed]

No sooner got my 2l sport immobaliser probs. sorted than daughter's 1997 2.5D LWB started on a series of electrical faults (return of nightmares from when I owned a Montego!!!!!!!!!!!!!).
I am an engineer not a 'Lecy but I usually get by. However these faults need some inside info. as I am getting nowhere fast. Have visually checked instrument panel & waggled tank cable & oil sensor wires to no avail.
1, oil warning light flashing but pressure gauge reads normal (have taken bulb out so can live with this).
2, fuel gauge suddenly stopped reading & low fuel light stayed on. A full tank had the gauge reading approx. half full & the light stayed out for a short while then back to no gauge reading & light staying on.
Have checked tow socket & various earth points to no avail.
Can't face dropping the tank without good reason as I'm sure it will end up as a major (& costly) job.
If it was mine I'd live with it (us ex-montego owners are like that, years of agrivation do it to you!)
So Its another plea for help.............