I haven't yet attempted to post a letter under the new size and weight pricing regime, but since it seems that many post offices aren't too clear on the rules I can imagine the chaos that is about to be unleashed. Not so much for senders of letters, but for recipients of correspondence deemed to have been incorrectly stamped.

It's particularly annoying to get one of those cards inviting you trek to the sorting office (opening hours to suit them, not you) to collect and pay (£1 plus the underpayment on the stamp) for a letter without knowing from whom it came. Sometimes it's a nice surprise - my husband once received a large cheque from someone who, having written it, clearly couldn't afford a stamp. To think he almost didn't bother to go and fetch it.