Went to ASDA in Leyton and near the counter they had Walkers world cup crisp single packs, priced at 30p each, but they scan through the tills at 10p each.
There were a few diiferent flavours and all of them scanned through at 10p.
Don't know if this nationwide but can't see why not.
Seems to be an offfline deal but not sure.
There's some nice flavours if haven't tried them yet.
Checked on the HOTUK site but couldn't see a post for single packs.