The Windsor, Stonehenge and Bath tours are very rushed. Below is the Premium Tours and Evan Evans Tour schedule. There are onl 3 main operators running this tour daily (Evan Evans, Golden Tours and Premium Tours), everyone else is an agent. (Gray Line tours are operated by Golden Tours)
If you really just want to see Stonehenge and Bath, forget these tours and Windsor, you can easly see Windsor by public transport from Central London independently. Anderson Tours run a daily tour visiting just Stonehenge and Bath. You get the whole afternoon in Bath, much more satisfactory than the glimpose you get with the other tours.
Premium Tours
08:15 Depart Victoria Coach Station Gate 6
09:30-45 Arrive Windsor Castle
11:40 Depart Windsor
13:00 Optional Lunch at traditional British pub
14:00 Leave pub
14:20 Arrive Stonehenge
15:10 Depart Stonehenge
16:10 Arrive Bath - Panoramic tour
16:15 Enter Roman Baths
Free time
18:00 Depart Bath
approx. 20:30 Arrive London
Evan Evans
Leave London (VCS) @ 09:00
Arrive @ Windsor @ 10:00
Leave Windsor @ 12:00
Arrive Stonehenge @ 13:10
Depart Stonehenge @ 14:00
Arrive Bath @ 15:15
Depart Bath @ 17:00
Arrive London @ 19:30