Lorraine, the most comprehensive list of festivals and such in England that I've come across is from the magazine Folk Roots. Their website address is http:/www.froots.demon.co.uk/ if you click on the words 'festivals listing' or something similar, on their homepage, there's a list in date order of all sorts of stuff, including Glastonbury Festival. Glastonbury's a big festival, thousands and thousands of people, a lot of the others listed are much, much, smaller, which is what I happen to prefer, it depends what you want. There are links or telephone numbers for each event.

The Tourist Information Board's site might also have something of interest. I had a bit of look through, they mention traditional events such as well dressing, also music and all sorts of different things.
That was after I'd finished looking through a Gloucester area website wondering why I couldn't recognise any of the names, then realised it was Gloucester, Massachusetts.
That's at http:/www.travelengland.org.uk/ (the english one not the american one)
I've never been to Salisbury, Bath's a lovely place, pretty, interesting and clean. I hope you find something that you enjoy, and that the weather's kind. Have a good trip, Liz