I have 2 disagree strongly with the lies the local has written about coledale. I have been camping at Coledale at lest 15years and a member of the surf club for almost as long.
Yes the camping ground is fully booked during the period of Christmas and New Years, and most school holiday it also becomes pretty full.
I also have to say I have never experienced, the muddyness. Coledale is growing in popularity, but is still less packed then Austi. Hope this is more helpful.