AKICILJ: Queuing for Prom Tickets?

The Ukulele Orchestra of Great Britain have a Prom Concert on Tuesday night. It's quite late - 10 until 11 - and there aren't any decent paid tickets left. So I'm inclined to turn up for an on-the-night standing ticket. These apparently go on sale for £5 an hour before the concert starts; does anyone have an idea of how long before that I should realistically arrive to be sure of getting one?

And is anyone else interested in coming?

It's Drink Wine Like A Pirate Day!

At least, according to my local off-licence. Arrrr!