Hey all,
The dub's playing up and pissing me off again

The problem is the oil light and buzzer keep comming on, now I know this is a common fault, But here's the background of the problem:
It started about 5 months ago, it would come on intermitently at about 5k revs, and when you dropped below about 2000 revs it would turn off again, this then stopped for about a month, then I fitted GTI clocks and no buzzer for about 3 months... untill today

I thought the fault was with the old clocks, but I must have been wrong

Now it comes on when I go about 2000 revs, and unlike before it will not go off without turning ignition off and back on..
Any ideas as to what this might be? am I advised to replace the sensors or check them first some how? it's a 1.3 BTW, any help appreciated! thanks peeps.