Ovenpride, brilliant stuff. Paint the stuff on the inside of the oven, put oven racks in the bag that comes in the box, put some of the stuff in the bag and leave...I usually leave for longer than the reccommended time, rinse off = clean oven.
Un clip all the racks inside. Soak a dishwasher tablet in a mug of boiling water for a few seconds to soften it and then use it as an eraser to rub away all the crap, this is fantastic on the oven door especially.
Soak the racks in boiling water with a dishwasher tablet then put them through the dw if you have one, if not give them a feeble scrub, you won't need to scrub hard ime.