Need some advice please

[Kaponeoly]

Hi folks, new here, greetings
So had my caddy maxi 1.9tdi for 10 years now and I'm totally attached to it!!!!, love it
265000 miles
Recently engine oil pressure light came on and at the same time got a fuel leek from around the tank area
Took it in, mechanic did a pressure test, said that pressure was low.
He said it wasn't a faulty pressure gauge
He dropped the sump,,no sludge in sump
He changed oil pump, no better
He then put in thicker oil, no better
Engine sounds good, not loud in any way
Fuel leek wasn't that bad then so carried on driving it.
Broke down Christmas day on the m60
Recovered by AA.
Car just slowed down and came to a stop
No change in engine apart from the idle and stop, engine still starts as normal and sounds good.

My question
AA guy told me that vw caddy throws oil pressure warning when there is an over fueling problem and that he thinks that because the engine sounds good and because of the fuel leek it is probably an over fueing problem, maybe with faulty injector.
Problem is the fuel leek is comming from around the tank and is pretty bad now a after breaking down
My mechanic said a rubber washer in the hose above the tank needs replacing for the leek and a new engine is needed for the warning light because 265000 miles there's no point stripping down to find problem.

Is there any chance that the feul leek is related to the oil pressure light in some way
Would be good not to have to buy a new engine
Sorry for long msg
Any help would be appreciated
Thanks