If it is any comfort Graham, you are not alone.
I get two or three surcharged items a week due to senders' putting incorrect postage on them - and this some eight years after the system changed. In my case I pay the charge (which by the way includes a ^1 handling fee) and where appropriate bill the customer. It saves a lot of hassle with people phoning up claiming to have sent something which I haven't got.
A useful tip if anyone is unsure how much to put on an envelope is to take it to a Post Office. If they get it wrong, and they do, the fact it has one of their gold printed stamps (soon to change colour) means it will not be surcharged and the matter taken up with Post Office Counters later by Royal Mail.
The entries are still winners in my view, and I will publish them in separate threads. The important thing is that both of them have made a very real difference in helping to bring people onto the trains - "putting new life into local lines", which (if I recall correctly) is ACoRP▸ 's marketing line.
All that said, I totally agree they
are winners and presumably as the entries were not looked at, a lot of the groundwork for next year's entries is already in place?