I went to one in the summer. It's not dirt cheap, prices were £20 for all womens skirts, £30 for all knitwear, and I think £15 for all tops.
I've had better in the actual sale online. Definitely worth a look though - there was no scrum at the one I went to.
And if you're a sad Boden groupie it's quite a thrill to get a big Boden carrier bag
Though as I said at the time, digging through scabby boxes in a smelly scout hall does somewhat take the mystique off Boden clothing. Kind of makes you wonder what the fuss is about.