I came over for four festivals in August this year. Broadstairs is Ideal for fringe events. Spread all over the place.
Whitehorse I paid for an OAP ticket Glad I did. Met the aritist close up. Very nice small festival cheap as old chips but worth every penny. Not really any fringe there, just the late night sing-around.
Towersey. Well, Towersey was expensive but again worth it. You need ticket to get to the main concert area and the Ceilidhs. There is a small fringe at the pub and the barn, but really it all happens in the main area. and it was very good too.
Wallingford Bunkfest is a fine, very fine fringe event. Lots going on. Free workshops. There are concerts if you're that way inclined too. But mostly a fringe affair that really works. Need a ticket for the Ceilidhs though.

I enjoyed myself meeting old friends and making new ones.

Chas