For an amusing parody there's "Awayday," the Kipper Family's take on Gaudete. Hilarious!

Cheers for mentioning Maddy singing The Holly and the Ivy, Dave, one of my very favourites (and which has a riff! ;-) ), but no-one here will ever hear my most treasured carol in the way I did. 'Twas on a freezing cold December afternoon in London in 1973. Hundreds of us commuters had been evicted from London Bridge underground station after the IRA had issued a bomb warning (there was no bomb that time, by the way). We'd been standing around for ages in the cold street hoping to get back in when a very small lady, who looked about 80, struck up in a stentorian voice in her cockney accent with the Cherry Tree carol. It was so uplifting and the gloom among we frozen hordes was immediately lifted. I've never forgotten that, I know no-one can ever hear what I heard that afternoon, and I've treasured that memory for half a century!