I did this route with the RX8OC a couple of years ago… a superb drive, even in the deluge we had that day.
Take the A419 to Cirencester, Take the B4425 to A40, Turn right on to the A40, then left at the Burford Travelodge (There is also a large pub on this corner). Thru Burford Main street and follow the A424 through to the A429. Turn right onto the A429 and then left on the B4068 Follow the B4068 to the A436, then turn right and head towards the pub. The Air Ballon-Birdlip
If coming from the west, take the A435 from Cheltenham to Cirencester - nice wide twisty road. Now reasonably empty as most traffic takes the A417 dual carriageway.