It doesn't look good, I'm afraid. Here is the advance sign on Dermody Road that you drove down to turn right into Leahurst Road : -
Find local businesses, view maps and get driving directions in Google Maps.
and here are the restriction signs themselves, mounted far too high in my view but they get away with it, I'm afraid.
Find local businesses, view maps and get driving directions in Google Maps.
You may well have driven along Leahurst Road in the past without penalty, (1) the restriction has only been there since the GSV view of September 2022, and (2) you drove down there outside the restricted times.
What I suggest you do is list here the PCNs and their date, and date received. Representations have been won in the past based on the appellant only becoming aware of the restriction on receiving the first PCN on a certain date, with the others dated after PCN 1, but not being received until PCN 1 arrived.
There may be other representation and appeal arguments based on Lewisham mismanagement of the enforcement process, so wait a bit to see what is suggested.