I'd suggest the Nurburgring myself

sorry for that Keith, i have a certain fondness for the Massif Central, the Alps, Cote D'Azur and the Pyrennes, but i'm sure you've done all that, so why not try Croatia (dirt cheap) or i really enjoyed riding round mainland Greece away from all the tourists, again v cheap and v friendly, but a bit of a trip getting there.
Or how about further east in the Alps into Austria and Northern Italy. You could try all the high mountain passes in the Alps, the highest in Europe being the Col de la Bonnette at just over 9000 feet, you can link that to another 6 or 7 passes.