In my local Spar in Sheffield today and saw they have 12 packs of Pepsi for £2. They also have 6 packs for £2, which is good. Anyway, 17p each this way, about as cheap per litre as the 2l bottles when they're on offer, without the going flat. Don't see why it wouldn't be nationwide, but if it isn't, my apologies.
First post, go easy! :)