I did this route the other day but started from Stonehenge. Scenic & good fun!
Route starts in Wootton Bassett, but can be picked up anywhere on the loop. Runs through historic Avebury, then along a superb open road to Devizes. Out of the town through the country and onto the fast open Salisbury Plain. Passing Stonehenge turning north through picturesque Savernake Forest and into Marlborough. Returning to the start over the twisty Hackpen Hill, with great views at the top over Wilts!