I used Ovenclean and they are amazing. We were selling our house and the oven was a large range type one which was well, well used. It came up like new and no chemicals were used in the house as they took the loose pieces outside to soak/clean. Inside the cooker was cleaned by mainly elbow grease. As I am an asthamtic I was a bit cautious about any company that sprayed the oven with chemicals then left it for a couple of hours then returned. With Ovenclean there was no residual smell and the results were incredible and I would use them again. Just google Ovenclean and put in your postcode and they will give you the number of the nearest operator.