Need private tour company reco for Bath-Oxford

You might want to look at these from London Walks for some Harry Potter adventures.
www.walks.com/London_Walks_Home/Harry_Potter/default.aspx. One is a private tour with a taxi driver.
They also do some out of London trips to the other places you have mentioned.

Have fun.

bath and oxford were our top two choices for day trips, too. we're doing it on our own after comparing time and money spent for the guided tours (time was the bigger factor--money we can earn, time is limited!) i highly suggest looking into this yourself, as it does save a lot of money AND time. a comparison--a bus tour from london to bath and stonehenge--12 hours long. 1.5 hours in bath, 30 minutes at stonehenge--the rest on the bus. we'll have 7 hours in bath not including the four hours we'll be gone on the stonehenge part of the tour we are taking, and there are free guided walking tours set up by the mayor's office (check out visitbath.co.uk). we pre-purchased tickets to bath from paddington station through first great western; the prices run from 9.50 pounds to 24 pounds per person each way depending on time of day and day of week (we ended up paying 31 pounds per person round trip, as the return trip was much less expensive). we are then doing a mad max half day tour out of bath, which included lunch in lacock, that might satisfy your costwolds need (as in 'it is a quaint little english town') and i think part of some of the harry potter movies were filmed there. oxford is even easier on your own--it is a 45 minute train ride costing 15 pounds per person for a return trip. have a great trip, and i hope your daughters enjoy themselves as well!