Whitby is magnificent at any time of year, but unfortunately, as you would expect, it is a victim of its own success. For such a small town where all the good bits are in one small area, accommodation and parking are at a premium. But well worth it. Lots of folkies have made it their home in the last 50 years so that tells you something.
There are at least 2 folk festivals and others, as well as the Regatta. It would take several books to extol all its virtues; ah I see somebody already did that.