Don't bother with Hunters, over priced and not made for normal human beings who have any hint of calf muscle. Get wellies that you can get on and off comfortable in a confined space (Hint: a tent
).
If you are wearing wellies for and extended period your feet and lower legs will sweat like a waterfall so get decent knee high wicking socks (multiple pairs for the period of the festival obviously
) that allow you to fold a good portion over the top of the wellie to stop wellie-whip (you'll soon know what that is if you don't do this
)
Also try to get wellies that will allow you enough room to fit a sports or walking insole as that will make any length of time in them far more comfortable and try not to wear them all the time to allow everything to breath
Me? I've been going to festivals for 28 years (every year to multiple festies) now and as hinted by Avenged7Fold above have found much better alternatives to wellies that mean I don't wreck my feet