if you are thinking of going to Durham (which I think is at the end of July), you might like to carry on up into Scotland: there are lots of festivals over the summer months: quite a number of them are listed in the 2013 TMSA (Traditional Music and Song Association of Scotland) calendar, which is currently in preparation, but should hopefully be up on their website in the next few weeks:

http://www.tmsa.org.uk/

Most festivals include a good mix of performances, sessions and workshops so you an do a bit of everything: if you want to perform, some of them have Open Mike sessions too.
You might also find this website useful for anywhere in the UK and Ireland:
http://www.ukfolkfestivals.co.uk/index.php