New to the forum but been an avid reader for quite some time, quite alot of my car issues have been answered by previous threads but I'm wondering if anyone can shed some light on this one...

Car is a 2.0T FSI S-line with DSG.

-Bought it last year and the oil pressure light came on. Got the car recovered, back to the Audi specialist I bought it from who checked it all, took the bottom end off, said there was some damage under the car that must've been caused by a speed bump or similar before I bought it. So, parts replaced under warranty, engine flushed, filters replaced etc and fine until now.

-Pressure light came on, got the car recovered(no warranty) to another place who checked the car over, unblocked some stuff relating to the hydraulic lifters, flushed it and car running fine...except a noise coming from the top end.

-Took the car to Audi who couldn't locate the noise, wanted a fortune to strip it so I took it to an independent engine specialist who stripped it down, top and bottom, found the camshaft in a right state and replaced all the associated parts(casing, gaskets etc). Said it was all completely worn. Engine is running great now. They also had the bottom end off and said all was fine.

-Thermostat isn't working properly now. Engine sits around 60 degrees and only rises to 90 in traffic, never goes above 90.

-Driving the car today and the oil pressure light came back on when the car got to optimal running temperature. Pulled over immediately, turned the car off and let it cool down, checked oil, all fine. Switched it back on after cooling down and its running fine now, no light.

Apologies for the story but any ideas? There was no signs of wear or blockage in the bottom end. Could this be valve/sensor related or similar?

I'm worried that the oil pressure drops when the oil heats up and thins out. This has cost me an arm and a leg so far.

Cheers in advance