Motor oil spill on car seat upholstery!

Hello,

We had an accident with our car oil which was living in the boot of the car, tucked away in a recess. Unfortunately one of us left the lid slightly undone and for weeks the oil leaked out slowly! It travelled all the way up the boot into the back of the back seat and made its way through the foam and out the other side onto the surface of the seats upholstery. Unfortunately it wasn't discovered for some time so the stain has already set. We tried bicarb soda and that absorbed a bit of the oil however there is a large noticable stain.

I've had one car detailer suggest the only way to rid the problem is buying a whole new back seat! We realise that the stain probably won't come out now but if we can improve it at all.

Can anyone recommend a product that may clean it up? Or a company near Sevenoaks, Kent that may be able to clean it professionally?

Thanks in advance for any advice you may be able to give.

Cathrtw