Cheers, I use OT8 from them on oil but there must be something cheaper as it would cost a fortune!!!
Also it states this on the website:
For best results or for when using on larger stains, cover the treated area with polythene sheeting − ideally making a tent − and keep in place for up to a week. Ensure the area remains damp, but not flooded. Doing this provides a warm and damp environment, giving the bacteria used in Bio TA the best conditions to grow and digest the oil into carbon dioxide and water.
Oil stains degrade Tarmac and Asphalt, leaving behind an etched surface which appears as a dark stain − this cannot be removed.
A week!!! Don't think the school would be too happy about that. They must use something on motorways that is cheap and fast acting after a crash etc