After all the positive replies on this I went for a Salter EK4548 Dual Air Fryer, Double Drawer which arrived this afternoon. Cooked my first meal in it this evening, jacket potato and a couple of lamb chops (I used the microwave for the beans).
It was brill, took 30 minutes and was slightly overcooked, I will try 20 minutes next time. Had to wash the two drawers afterwards but they're non stick and the oven has got no dirtier.
Definitely looks like a good investment.