Pop over the road to the Chinese supermarket and get a box of deepio. About 9 quid for a huge box, its like washing powder. That and hot water. Sooner you attack it the better.
As it's likely to end up in the drain, then as said above you don't want to be putting anything toxic in deliberately or you could be prosecuted. So washing powder is a good suggestion - it'd be no different from you washing (a lot of) oily overalls in a washing machine. Cat litter and sand work well for soaking up the bulk of it first though.