The existing Sunday service for the 49 bus which runs between Swindon and Devizes via Avebury is by no means brilliant - every two hours (with a three hour gap in the middle) ceasing at around 5.00pm so can't be that expensive to run. I've used it myself often and I can assure everyone it is never empty, people pick it up in Devizes and Swindon getting on and off in between. It is also a double decker so a superb way to see the Wiltshire landscape.