Thanks for this - I've paid it a visit. This whole thing seems very understated, surely increasing the chances for a lucky few.
I'd visited 8 stores around me in the end over the last few days (Blackheath, Eltham, Charlton, Greenwich) and I didn't see any obvious promo material. Two stores had no Brooklyn at all; two more only had bottles and rest had, at most, two packs. It's very odd.
So I have a pack from my Co-op tour and one from your shop showing the promotion. We go again next week, I suppose. At least it's more drinkable than that sweet Brothers stuff.