Sorry to take a while to get back to you, here are the rotes from Bike Mag.
Trip 1
Swindon to Highworth, then to Lechlade, across to Faringdon, across to Wantage, stay on the A417 to Streatley, then the back roads to Chieveley, then up to Wantage, and use the back roads to Lambourn (or a short cut straight to Ashbury) and then across to Ashbury and back to Highworth.
Trip 2
Swindon to Lechlade, jump on the A361 and stay on it until Daventry, it is a long straight road, one of the old roman roads (watch for cops and cameras).
Trip 3
Wroughton onto the A4361 to Devizes then onto the A360 round to Amesbury and onto A302 and up to Tidworth and stay on this road to Burbage, jump on the back roads to Hungerford, and stay on the back roads back to Wroughton.
If you get through these and want more I have some more that are over towards Cheltenham and then some over towards didcot as well, so making it a little longer, I know the roads around Didcot are nice and smooth roads as I work over that way (until Wednesday) and ride to work 90% of the time.
Ride cool and ride smooth.
Ride to the midnight sun and back again.....