Hadleigh Farm, Essex, was confirmed as the venue for the Olympic games in London in 2012.  According to the organizers, “the route weaves through grassland, woodland and masses of the Hadleigh castle countryside. Two major hills feature, separated by a valley, which will provide technical climbs and descents.”
The trails are about 45 minutes from the planned Olympic Village and has lots of room for spectators.
Hadleigh Farm replaces the original venue near Benfleet after organizers and others complained that the chosen trail was too flat and simple.  Check out the area via the Essex County website (if it’ll load) or more info from the UK Salvation Army, which owns the land.