Just to add. I took a video to show the 2 contradicting posts with the bay. It doesn't seem to be split up
https://filebin.net/05787xc2mctcx2mh
Well, yes, it is a complete nonsense, and I would think is a slam-dunk appeal at London Tribunals. Normally when we have seen things like this, it is two bays with a bay divider consisting of a double-dashed line perpendicular to the kerb, and one sign for each bay. Many people miss things like this, but here there is no bay divider. So you should submit representations on the basis that you parked and went to the nearest sign that told you you could pay to park by phone, and that is what you did. Attach a photo of the sign.
Don't be miffed if they refuse your reps, because councils ruthlessly game the system to get the money in, so refuse almost all informal representations and re-offer the discount. They do this because they know most people, (>95%), then just cough-up believing the council are right, and also don't want to risk the full PCN penalty.