What's the best way to travel/tour Bath and Stonehenge from London?
There are bus tours that cover both. Evans Evans Tours has two types of tours: "classic" where everything is included, and "select" where you basically are paying for the transport and everything else is optional (Probably better for an independent traveler.) I've never taken a tour with them but they have a good reputation
I did Bath on its own....by train. Left London in the AM and returned at night. The train station is bath is a few minutes walk from the center of town.
I'm traveling there in two weeks and will probably do as Rick suggests: take the tour from London with my luggage then leave the tour in Bath. I'll be spending two nights there and will take the train by myself back into London. From all the reading I've done, it doesn't seem necessary to stick with the tour once in Bath. Bath provides their own tours around town but I guess I'll find out.
For a real trip to Stonehenge, look into Astraltravels "Special Access" tours. They take you to Avebury, Silbury Hill and get you into Stonehenge inside the barriers. This is before or after the place is open to the public. We had a whole hour to talk to and touch the stones. Good guides, about 20 tourists. Leaves from a hotel near Victoria Station. Reserve from US. One of the highlights of our trip last year.