Update - I appealed online, giving Lewisham the RingGo reference for the payment I made. Today I got a letter saying they can't find that transaction so the PCN stands and I have to pay or appeal further.

They're having a laugh - that transaction on RingGo is the one and only time I've ever used the app, and they can't find it on the RingGo system?

What is interesting is that when I appealed I was told that if my appeal was turned down, I'd have to pay the full amount of £60 (which is reduced to £30 if you pay within 14 days). With today's letter they said I could have another 14 days to pay the reduced rate. Hmm. Makes me wonder if rejecting the first appeal is standard practice, if they can find any wriggle room at all, in the hope that the driver will get fed up and pay the newly offered reduced rate they thought they had lost out on.

The other frustrating thing is that I can't reply to today's letter with my proof of payment. I have to wait until the (new) payment window expires, at which point they'll send another letter and then I can appeal. This is barmy. Again, how many people give up and just pay the £30 at this point?