CU Spaceflight Landing Predicton - Similar to wyoming however is quicker to run and has more variables such as ascent and drag factor so you can tailor make your predicted trajectory flight path.

University of Wyoming's Balloon Trajectory program - Assumes about a 270m/min (4.5m/sec) ascent rate and 4.9m/sec (low altitude) descent rate.

Near Space Ventures Flight Track - Online version of Bill Browns original BASIC Balloon Track (appears to just use US Weather Stations) Try WATTISHAM RAF(03590), COLTISHALL (03495), HEMSBY (03496) as nearest WMO stations to Cambridge.