I went to M&S yesterday and found some long sleeve baby vests on the full price shelf priced up at £9.50 but scanned in at £2.00.
If you do look for these vests you should be able to distinguish between the new and old packaging.
I don't think the staff are aware of the promotion.
Seriously a bargain..........you never have enough baby vests.,,
let me know if you want any more information or codes