"Festival ... Of or pertaining to a feast ... A time of festive celebration" (Oxford English Dictionary)
Banbury Hobby Horse Festival (Oxfordshire)
"Ride a Cock Horse to Banbury Cross, to see a fine lady upon a white horse" begins the famous nursery rhyme. Banbury's hobby horse festival began in 2000 to celebrate the town cross and hobby horses (which is what a cock-horse is). It is to be held each year on the last weekend of June, and features a number of events, notably cock-horse racing.
Read more about it here or visit the organisers' web-site.
Golowan Festival, Penzance (Cornwall)
Starting on the Saturday nearest St John's Day (24th June), this derives from the midsummer Feast of John (Gol-Jowan) and is now a ten day festival which culminates in Mazey Eve, Mazey Day & Quay Day.
Contact +44(0)1736 332211 or visit the organisers' web-site
Jack In The Green Festival, Hastings (East Sussex)
Held on the first weekend in May with Jack's appearance on Monday. The Jack is the symbol of the summer. There is debate on whether it represents a garland from the 17th century or if the tradition is much older and more significant. There are now around 1,500 participants, 10,000 watching the procession, and 5,000 attending the finale in the castle where the Jack is symbolically slain. Also live music and celebration over the weekend.
Contact +44(0)1424 429154.
Rochester Sweeps (Kent)
Held on the first weekend in May, this originates from the Industrial Revolution when chimneys were swept by small children, or Climbing Boys. Chimney sweeps would perform in a colourful processions on May Day and collect money at a time of year when work was scarce. Jack-in-the Green was the central character in the procession and helped them to raise money without begging. After the Climbing Boys act of 1868 and the development of the chimney sweeps' brush climbing boys became redundant and the Sweeps' Day was no longer celebrated. In 1980 the Rochester Sweeps' Procession was revived. Now the Festival lasts for five days with music, ceremonies, exhibitions, dancing and the Sweeps' Procession. Rochester, Kent.
Contact TIC +44(0)1634 843666.
Whittlesey Straw Bear Festival (Cambridgeshire)
Held in early January. Contact the Straw Bear Society, Society Secretary, 5 Hammerley Drive, Whittlesey PE7 1NE +44(0)1733 208245, or look at their web-site.