AmberNectarine I have, queueing does start early, mid afternoon I think, but unfortunately it won't really guarantee you prime seats, it's not first come first served. The big block opposite the judges is mainly all guests of the celebs, pros, invited celebs etc. The other prime seats and front rows usually get taken up by production staff tickets. If you've got a general public ticket, you'll most likely get the back rows or up on balcony. Unfortunately, you pretty much can't see any of the dancing from about two rows back, as the seats aren't tiered that much.
BUT, that all said....they do have some good seats they will need to fill, so you might get lucky, and the whole experience is just fantastic anyway. All the backstage, off camera stuff, before and after filming, it's true what the celebs say when they leave, everyone from the runners, production staff up to Claud and Tess are professionals and amazing from start to finish, on and off camera.
Glam wise, well dress code yes, definitely but wear heels you can walk and queue in. It's on an industrial estate and there's a walk down hill to the porta cabin loos. The dress code and the show itself where the glam starts and finishes!