Seems a strange way of going about business, but right now, the Vintage festival at the Southbank Centre in London this weekend seems to have tickets heavily discounted from the original price. I'm guessing that's annoying if you paid full price. But not bad if you didn't bother and have nothing on this weekend.
One such outlet is Time Out, which right now is doing tickets for Saturday for £19. There were Sunday tickets too, but that offer has just expired sadly. Bearing in mind the full selling price is/was around £60, that's a huge discount for the vintage-inspired event.
It is a limited offer, so get in as quick as you can if you want them. We'll keep our eyes open for a ticket clearance for other days.
Note: This offer has now expired.