New Bradwell allotments/ Ouse Valley car park, MK13 0AW. Entrance on the north side of Newport Rd, near the Stonebridge roundabout. OS map 152, grid ref: 823 416.
A 20 mile (avg 11/12 mph) anti-circular road ride through the rolling countryside to the north of Milton Keynes, with a halfway stop at the Salcey Forest cafe.
Here's the usual route, which can be adapted: http://connect.garmin.com/course/2399085