The home of the folkie on holiday.
Folk festivals are a relatively recent phenomena - commensurate with the revival (i.e. since the 1960s).
There are now festivals great and small, one day and whole week and catering for a variety of different styles. The Deal Maritime has an emphasis on shanties and is over a weekend, while Broadstairs is a fairly mainstream week long festival ranking alongside Whitby and Sidmouth.
The celtic fringes have had gatherings for a long time, some of which have evolved into the modern festival form. Many Celtic festivals are modern events making the most of the renaissance in Irish Traditional Music on the back of the phenomena which was Riverdance.