Whitby would be my no 1 recommendation. But be aware that accomadation at Whitby is at a premium. B&Bs, Hotels & self catering get well booked up ahead of time. Camping at the main festival site is for season ticket holders only (there is another temp campsite set up by Moor & Coast see This Thread, but this is filling up fast). As for Whitby week itself (Whitby Folk Week )if you want to see a lot of the booked artists then a season ticket is good value, if you just want to go to a few workshops & watch the dancing & "fringe" in the pubs, then you are probably better not getting a season ticket. Me i'm a season ticket man, I like to do a bit of everything.
Also there are many morris sides around the country who have dance out evenings & weekends of dance where you may see several sides dancing together. Most teams have websites which will detail dates etc. Most can be found here Morris Dancing.
Hope this is helpful.
Cheers
Les