WD40 is the best thing i've found for removing tar, spray it on, leave it a few mintues and then rub off the spots, you might need more on the cloth if they are stubborn, but it works better and is much easier than clay. Just have to wash it afterwards and then polish. 
Sandy
Hmm, interesting, never thought of using WD40, normally use Tardis. I was planning to give it a full going over at Easter, including applications of IronX, Tardis, followed by claying, polishing and waxing, as well as washes in-between the various stages. Setting aside 2/3 days under cover to do it all.