Found these on clearance in the Leigh store, no longer available to buy online so most likely a national clearout since the movies have long since been and gone. They had Sea Salt, Sour Cream and Cheesy flavours.

Best before is October 2016

In that store theyd moved most of them from the crisp aisle to where they put clearance things with bashed boxes, though these items were perfectly fine. Was just a few packs dumped in the crisp aisle though still.