There's a Travel Lodge on the roundabout at Middlewich 10 miles from Oulton Park. It's on the way to the circuit if you're coming from East Anglia too so no need to go out of the way.
Nothing to shout about (as they all are!) but better than attempting a 500 mile round trip and a track day in one go. There's a V power station on the same roundabout too :-D
Very comfortable and spotlessly clean rooms. Great value and about a 10 min drive from knockhill. A very nice local pub with very nice food. No parking for trailers but you can usually leave those at the circuit.