If you genuinely have low oil pressure, it's not a good idea to drive it and it needs to be checked at a garage. Low oil pressure can quickly cause disaster for the engine.
First things first though, give the sensor, which is to the top left of the oil filter, a wiggle at the connector as it could be loose wiring.
Then try a new sensor 7700417970 and sealing washer 7703062043. Seems these are quite cheap as eight quid has been mentioned.
It seems that this is more likely to be the problem than a genuine loss of pressure. If that doesn't fix it, get it to a garage.