Have just run my generator for the weekend it run out of oil, when I started it up there was loads of smoke coming out and it smelled of burning, is it ruined?
Most likely, yes. If you want to be sure it's dead drain/refill the oil, put some good (preferably non-ethanol, high-octane) fuel in it, and let it run a little bit and see if it wants to come back to life. But most likely it's toast.
I'd dump the oil that's left in it and refill it with the proper grade and amount of oil and let it run a while. Might be fine or it could be defective and in need of a warranty return.