If it's only happening when the motor is very hot then i'd suggest the oil is either shot, or the oil pump has some wear in it.
Oil grade could have a bearing on it to. 10W/40 will not hold pressure as well as 15W/50 when hot. If the oil is old then the problem could be worse.
If the light goes out when you rev the engine, i'd guess the switch is OK.
It could be worth asking to have the oil pump clearances checked whilst the bike is in for the service?

Thanks Guys

Nelly wouldn't a pressure check show up any faults with the oil pump ?:puzzled:

Yes, probably. Check the pressures were quoted on here a few days ago i think. Not sure off the top of my head.................

cold is something like 3bar at idle, 5 bar at 3000rpm
hot 1.5 bar at idle, 5 bar at 3000 rpm.

something like that anyhow. The figures are in the manuals. Moto Rapido should certainly be able to check and sort if required.