H, Just bought a NC30.

When there is still petrol in the tank but not much the bike is suddenly cutting out and without much warning but I presumed I needed to switch to reserve even tho I could still see petrol in the tank (not much) but this didn't work either the bike wouldn't start. Once I filled the tank up with a little more petrol it was fine again, the same happened again after I done about 80 miles ? Any ideas what could be causing this and where do I start ?

Start with the obvious.

Check that when the tank is switched to reserve fuel comes out...

Sorry to sound stupid - Where exactly to I check the fuel coming out from ?

Take the fuel hose off at the tap. Should be held on with a jubilee clip. Take that off and see if you get fuel when the tap is switched to reserve.
Your reserve pipe in the tank might be blocked.