Would you take the trouble to email the Cumbria Tourist Board (they have a website) and ask this question of them? I just had a meetinf with one of their people and suggested it was one of their jobs to compile a diary and tell people when they get asked.
   I have ntl cabletv internet access, so cant do clickies easily to direct you to places, but if you google on Cumbria folk music you will find a diary or two. I cant think of just what is going on in Keswick this weekend, but I'll make an enquiry or two.
    If you would like to read an interesting article on William Irwin the Keswick fiddler, there is a thread on the subject. If you type "William Irwin" into the refresh place, and set the timescale to three months or so, you'll get it.