Mini Clubman R55 Cooper S excessive oil burning all of a sudden
 

Car has 68k, Full dealer service History and was driving and working well. Started a 300 mile Highway journey with all the engine levels good and oil and filter replaced the same day. After 291 miles of driving the oil pressure warning lamp flashed on three times in about 15 seconds by which time I released the throttle and whilst trying to get towards the hard shoulder of the M4 the engine lamp came on. I shut down the engine and stops car. After about 5 minutes I got out and checked the engine oil and found that the dip stick would not register an oil reading. I put 3 lites of oil in it and that brought it to the half way mark. I started the engine, oil lamp went out but smoke coming from exhaust especially under load. Checked turbo pressure side no oil, checked inside intercooler inlet hose and no oil residue either. Any ideas? Could it be PCV breather fault? To burn nearly 4 liters of oil in 300 miles and 5 hours of more or less constant driving is not normal for a car that was performing ok up until that point. Would love some Advise!!!!!