Hi Ian,
I woluld try white spirit first, test in an inconspicuous area first to test for colour removal and possible damage. If no adverse effects proceed.
If not try prochems solvall or solvex spotter or POG from woodbridge. POG works for me every time on oily stains a little expensive for a one off job though at over £50 for 5 litres.
You can probably pick up a 1 litre container of solvall/solvex for under a tenner!
Hope this helps,
Jason.