Recently looking to oil my decking and found cuprinol decking oil on offer at Screwfix. It comes in Natural Pine, Oak, or Ceder, and its one of the better products for decking. Some of the others only last one season.
This is the big 5ltr tin, not the smaller 2.5ltr one. B&Q are charging £26.99 for the smaller tin, so this is a really good deal.
Not sure of the expiry date