Phew, I'm glad cause I'm not usually one to stir the pot or go out of my way to cause trouble

Check out what the PO has to offer, but I buy all my packaging from an eBay seller & they are way less expensive than the PO (it also means I'm not familiar with all the PO terms & codes though ).  For items that are only marginally too thick for a large letter padded envelope I use these boxes 221181290924 and they are brilliant as they still offer good protection and come in a variety of sizes.  Hopefully they might do the trick for you too.  And yes, definitely ask for a card.  I was told they are not supposed to give them away - as they handed me mine , but it's less work for them if you have already pre-tested and as mentioned, if you check first, you have the opportunity to re-pack.