How do you define a "big" festival?
Cambridge is "big" in folk circles (and increasingly unpopular judging by other messages on Mudcat) but it's tiny compared to Glastonbury, Womad or the V Festivals.
Sidmouth used to be "big" but isn't really any more (though some of those attending like to convince themselves it's still "big").
Priddy is "big" for the West Country but not on the national stage.
Others are certainly "small" and proud of it.