My other car is a MINI!!!!
you better hope its the sensor.....
oil pressure warning lights are there for a reason, loosing oil pressure is seriously bad news.... and will end up with a seized engine.
if the light comes on you really need to kill the ignition ASAP before any damage is done, a momentary flicker could be acceptable when cornering hard, but any continous display of the warning light is bad.
have you checked the oil level? what sort of condition is the oil in? black and sludgy? or clean and smooth?
when you say the car wont start at all, will it still turn over?
i managed to blow up a 205 gti 1.9 motor a few years back, which would still start and just about run at the time, but the next morning it had set itself solid, and never did turn over again.
good luck! hope its just a sensor