One thing you can try Andy
is Tar Remover, the only thing
you would have to do, is to apply to the affected area Andy, and most
importantly you will need to leave it on the paintwork for quite a long
while, to soak into the paint. and keep reapplying as it dries. it will
need to soak the area for about 1/2 an hour. And then scrape the
paint off with your thumb nail Andy.
The Tar Remover these days is a little weak, so you have to leave
it on tar spots for about 5 minutes to just remove some tar spots.
Another thing to remember Andy is that the car paintwork needs
to be wet, for you to be able to remove anything without scratching it.
I hope this helps Andy, if not try Carb Cleaner, just a quick squirt
to see, but don,t leave that on at all, just a quick try.
Let me know how you get on Andy ok
All The Best.