I tried every way possible to get oil pressure without resorting to removing the pump..... I can confirm that on bmw 6 pots you can't do it! I removed the sump and oil pump, made a mess of my garage priming it with petrolium jelly and oil, after 15 secs of cranking it registered full pressure.

So a job done properly is the best way it seems! Happy now knowing i'm not risking damage to my engine.

Cheers again.