My girlfriend and I traveled to London in December, 2012, and we wanted to take a side trip to Stonehenge and Bath (and also Windsor if possible). Although we prefer to travel by ourselves rather than to go on a tour, after some research, we decided that it was cheaper and more efficient for us to go on a tour due to time and budget constraints.
We decided on Golden Tours over the other companies because
1) it was the cheapest of all the companies (only about $105 per person, all admissions included)
2) it offers pickup close to our hotel
3) the reviews on TripAdvisor are pretty favorable
Going in, we understood that the time at each attraction would be short and that a lot of the time would be spent on transportation.
We were supposed to meet at St Pancras Renaissance at 7:20-7:35; our tour guide (who was wonderful; it was a shame that I forgot her name!) showed up at around 7:40 and directed us to a tour bus. However, the bus had some mechanical problem so our tour guide promptly got us taxis to the bus terminal for no extra charge. This was very fun for us as this was the only time we got to ride on the black cabs in London!
The bus was spacious and comfty, and the tour guide was very courteous and accommodating, even to those tourists who were late (be on time people!). No one was left behind in any of the attractions. We spent about 90 minutes in Windsor Castle, 60 minutes in Stonehenge, and about 100 minutes. While it might not seem like much, my girlfriend and I had enough time to tour the State Apartments and St George's Chapel. We even checked out part of the Changing of the Guards in Windsor Castle! The time at Stonehenge was also sufficient (it was freezing cold!). However, we do wish we could've stayed longer in Bath, as we only got to tour around the Roman Baths and didn't have enough time to explore the wonderful town of Bath. If you are not interested in Windsor or have more time, definitely spend more time in Bath.
As for food, we did not purchase the lunch option, and instead of trying to sell us lunch, our tour guide was very nice and recommended some cheap options in Windsor; the sandwiches at EAT was delicious!
We would definitely recommend this tour to everyone who's short on time and wants to visit all these places; it's the most time-efficient and cost-effective way to visit all these places in one day. Thanks Golden Tours and our wonderful tour guide.