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the test track at MIRA and the bowl at millbrook proving grounds are Ideal. Rockingham of course and there is also the karousel at the nurburgring in germany.
There is a high speed bowl in France, I have driven on it twice and it is around the size oh Millbrook or maybe even a little bigger. Name escapes me at the moment but can find out if you need to know.
Having a go on the Rockingham oval on Friday, which should be interesting.
All of the above are good options provided you don't mind a modern circuit. If you want an older one with more character, try Montlhery (near Paris). Awesome place, lots of character and history, and more than a little bumpy!
If money is no object, why not try Nardo in Italy? I spent a happy 24 hours there in the 80s acting as service for a record attempt. Great fun, new tyres and fuel every 45 minutes! Didn't get to drive it though.