I'm staying in London for two weeks in the fall, but I'd like to visit some of the surrounding cities (Bath, Stratford-upon-Avon, Liverpool, York). I've found day trips through Gray Line Tours, but I was wondering if there are any other services that offer similar tours.
All of the places you have mentioned are very easy to get to yourself. My suggestion would be to either use the train or the bus http://www.nationalrail.co.uk/ and http://www.nationalexpress.com/home.aspx
Once you are in a town that you want to be in, then you could look for more specialist tours such as http://www.bizarrebath.co.uk/ or http://www.stratfordtownwalk.co.uk/
Hope this helps. almost 9 years ago