Free Traffic Legal Advice

The two bays are adjacent to each other, and the boundary between them is correctly marked, (the double-dashed line perpendicular to the kerb). In addition, the signs seem clear enough. So it's a bit of a puzzle as to why you didn't see them. Did you actually go and look at the signs at all ?

As against the above, the two signs are not ideally placed, because guidance on cases like this where two adjacent bays have totally different restrictions, is that the signs for each bay are placed on a single pole at the boundary of the bays, and arrows used on each sign to indicate applicability. However, the council are very unlikely to give way, so you would have to take them to London Tribunals and risk the full PCN penalty. If you're OK with that, then use the poor signage argument I have provided above.

There may also be a 'technical' appeal based on council mismanagement of the enforcement process which can win irrespective of the contravention itself. So wait a bit to see what might be suggested.

Is the vehicle yours, and is the name and address on the V5 up-to-date ?

The road is two-way and therefore you approached from the wrong direction i.e. you crossed into the opposite traffic lane and then reversed. IMO, an adjudicator would more likely than not find that there was a sign which was visible and which you should have consulted (let alone the Loading Only road marking) and find against you.

IMO, the sign is in the wrong place, not because there's a boundary with the parking place but because you spanned a borough road and reversed into a Red Route bay which should have been signed as such at its start.

The white road markings apply to both borough roads and Red Routes, the latter when the exemption applies for the whole of the Red Route restricted times(otherwise it should be marked in red). IMO, the Red Route sign should have been at the beginning of the bay i.e. when you left the borough road and entered the Red Route.

But I doubt this would win because ultimately you should have looked for the sign, and it seems you did not.

But you can submit reps at this stage with little downside financial risk and you might elicit a nonsense or otherwise defective response which might yet drag victory from the jaws of defeat.