Hi Craig, I would get your garage to closely inspect the oil supply to the turbo and through out the engine, you might have a blocked oil supply or return line to the turbo, or the oil pump might be only just putting out enough pressure to put out the low oil pressure warning light but the turbo needs more than the minimum pressure, The other thing to consider would be putting flushing oil in the engine and just let the engine tick over untill it gets hot then drop the oil from the sump as this will strip all the accumulated gunge in the oil ways inside the engine, as with all the failures youv'e had there is possibly metal particles from the failed turbo bearings and if they are not removed it will be like sand in the oil system and take out the bearings quickly!
nigel, July 2008