Hey Richard, my son and I are in Bracknell as well. You'll often see us in South Hill Park doing jumps over the ramp in the playground or Lilly Hill Park as it's right by the house. Best place close by I found is Lightwater Park just the other side of the M3 junction. Big flat field for speed runs and loads of forest trails with different surfaces, rock, sand, dirt, stone.... Free parking. Swinley forrest is OK but nowhere for fast runs and parking is a lot now. If you know anywhere else good, let me know.