We offer the choice of the credit card info (as Blott explains above) or a cheque for £200/$300.

If the guest chooses to pay by cheque/check then we do cash this and after inspection send a cheque back for the same amount. If we didn't cash it we would run the risk of a cheque bouncing if there was damage, and I have heard of this happening before unfortunately.

I would guess that the owner wasn't aware of the postal rate increase as that is easily done. I normally buy half a dozen stamps at a time and nearly did it myself. Sometimes the mail is returned to the owner if the postage isn't right. Happened to me once.