I have voted for December coz that's what we're doing lol. We've never been at Xmas time before, so it would be lovely to see all the Xmas decorations & shows (and I can then stop bugging DH about going at Xmas time!) plus it won't be as cold as January (hopefully) and we can't go in January anyway as DD's at school.
We'll be there 18th-21st Dec and I'm hoping 18th & 19th won't be *too* bad but expecting a mad crowd at the weekend. Yikes. What have I done? lol.