UK Car Repair Questions? Ask a Mechanic for Answers ASAP
The LS engines are known for roller lifter failure, camshaft bearings worn, and oil pump regulator valve jamming open, which gives no oil pressure at idle.
If they have gone that far with the engine with a strip down, MAKE SURE they replace the oil pump.
The regulator valve is probably the "real fault".
Have seen many.
How have you gone with your engine problem?
Do you need any further advice?