The Brooklands high speed track had the necessary banking but was not a true oval as there was a 'pinch' in one side so the cars and bikes had to sweep to the right on each lap.
There is a high speed track which is a perfect circle at Millbrook Proving Ground,Bedfordshire, England, used for endurance and time period attempts. Another test track is a sort of 'Tri-Oval' which is at the (Motor Industry Research Association) MIRA test facility in the Midlands, England. The race track at Rockingham, Corby, England has a Champ Car/Nascar oval but I do not know if they have allowed motorcycles and only part of the track is now being raced on.
Malcolm UK, England.