Bath - Windsor - Stonehenge Tour

Evan Evans tours.....http://www.evanevanstours.co.uk

They are out of London with several different pick up locations.

If you can possibly squeeze an overnight in Bath, you won't regret it. Then you could do the half-day Mad Max Tour that would take you to Stonehenge (and Lacock; we did the all-day tour, but wouldn't have minded skipping Avebury). That would give you some time to enjoy the Roman baths or other sites and just to wander around the city. Sorry, can't help you with Windsor.

I took the Evan Evans tour from London to Stonehenge. It was fair and accomodating, but a long trip because you are stuck on the bus, and Stonehenge is in the middle of nowhere. They ran a little behind schedule, but so was I so it actually worked out for the best.

I can highly recommend Mad Maxx Tours. I've done them three times with different groups for Bath/Stonehenge and was never disappointed. Didn't extend to Windsor.

We have used Evans Evans and Frames Rickards (years ago). Both were ok.

Mad Max is based in Bath and doesn't do tours from London which I assume is what you want.
Frames Rickards are no more.

From London there are only 3 operators that run Windsor, Bath and Stonehenge. These are Evan Evans, Golden Tours and Premium tours - everyone else is an agent for one of these three.

There is also a small group operator called International Friends that does the best quality tour in small 16 seat buses but this only runs a couple of times a week.

There is a good article on Windsor, Bath and Stonehenge tours at this url:
www.londontoolkit.com/tours/windsor_stonehenge_bath_tours.htm

I guess you are staying in London/if so you can easily get train to Windsor and do it on your own.