This is an archaeology forum and not the place for political tub thumping - it is no secret however that I am a supporter of public transport and I do think the number of cars whizzing around is madness.
Nigel does make a serious point above. Perhaps it is right that if bus services are not capable of paying for themselves, the taxpayer shouldn't be expected to pay for them. I can understand this point of view, but the essence of tax is that it provides revenue for public services, not all of which will be profitable.
Additionally, we don't get to choose (except in some limited ways) what our tax gets spent on. As a taxpayer I pay for schools but have no children. I would prefer our taxes not to be spent on Trident or on waging wars in the Middle East. Some of the revenue from our taxes (other than purely that derived from car tax) goes towards upkeep of roads anyway.
Then I started to grow in environmental awareness and it became 'my little bit for the planet'. The stark truth is that the planet is running out of fossil fuels and a viable alternative hasn't yet been found. I've never said to anyone not to use a car - only to use it less if possible. However, until there is a reliable public transport system to the places we both desire and need to get to, no-one is ever going to choose not to use their car.
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.
