Helen Love’s cover of The Ramones’ Merry Christmas (I Don’t Want To Fight) is the sound of Christmas as far as I’m concerned. You can download it at Filthy Little Angels. You’ll have to hunt for it on there but it’s well worth it.
For the most part, the chords are dead simple. I’ve put a C5 chord in because it’s more punk, but you can play a normal C chord there and it will sound fine.
The only tricky bit for beginners is the Fm. You can minimise the amount of finger changing between these chords by playing them this way:
Here, you’re keeping you second finger on the G-string and sliding it down to the first fret. It’s a little awkward but easier than completely changing your fingers around.
In the introduction to the original, the chords slide up from B to C a few times. The easiest way to recreate this on the uke is to play the C5 shape, move both fingers down a fret, play the chord and then slide your fingers up.