If the WD won't shift it pop along to your local paint supplier/motor factors and get a can of Pre-clean (there was a branch of Autopaint international in Withington last time I was down your way- its about £10 for 5 litres) it shifts anything, doesnt damage paintwork and smells jolly nice too! Also handy for removing felt pen and crayon from freshly painted walls ( my daughter Lola thinks she is Jackson Pollock this week)
Spot on advice - it doesn't damage the paintwork and re-polish afterwards.
MG Mark