Depending on the damage already done, tarmac must never be cleaned with the same chemicals used to clean concrete/paving etc, nor must you use a high pressure lance to blast at the surface.
There is a product called "Road Bio" - Oil Spill Detergent, from
www.opec.co.uk that emergency services use, but this is mostly for recent spills rather than oil stains, but it is possible to repaint with a black tar paint and filler if its not to bad, I think a company called "WATCO" sell this, but Im not entirely sure.
The best way to clean oil stains in block paving is replace with new bricks and rebed.
