Get some kitchen towels (dry quilted paper type) lay a couple of layers over the stain and then run a warm iron over it. It'll draw the fats up into the towel. Then wash with warm soapy water over the full seat area.
Greed got the better of me and one mars bar later I realised that I had a large chocolate stain on the driver's seat!
Before I attempt to clean it has anyone successful experience of tackling stains on tech cloth?