If you have any items you want to auction off, take them along to the Scout HQ at 10.30 am for listing in the auction which starts at 2.30pm. You can pick up your proceeds from the auction (or reclaim any unsold items) one the auction has ended (around 4.30pm).
Of course, if you just want to pop along to pick up a bargain then you're equally welcome! More details on the group's website.