Your oil pressure light is stopping on while engine is running have just changed oil and filter used correct filter and oil 10-40w?

If your oil pressure light comes on while engine is at an idle, maybe 10-40 is too low of a viscosity for your engine. I'd go to a 20-40 or 30-50 and see how the oil pressure does. make very sure you have the correct filter, some "factors" did for a while produce the wrong filter for certain vauxhall engines, these filters did not have a bypass and would cause light to come on, would couse catastrophic engine loss if not sorted. suggest recheck filter and obtain one from main dealer if not already done so. possible blocked oil pick up pipe in sump ,not uncommon if infrequent oil changes ..............PS i had this problem you made need to change the oil pressure monitor switch just on the top, front of the engine, it also appears to leak oil when the switch has gone!