I have a few problems with my newly aquired GTi Cab. Firstly, it has trouble starting from cold, and when revved to approx 3k rpm, the oil (pressure?) light flashes. After 5 minutes or so standing at idle though, the lumpy idle evens out, and the light doesn't come on. The offending light is as below: -

Could this be a fault with the oil switch, as it is fine at all other times, and is there anything I can get to even out the rough idle when cold. The car needs a service so could that be making things worse??
Thanks