Thx for the advice Hippo.
Yes, that is the sum total of the signage - 2 No Right Turn signs on the right hand side of the road from my pov. - 1 each below a double set of traffic lights, and nothing at all on the left side of the road.
The white car briefly crossing my path from my left would have had to run either an amber or red light to be in that position while I was already moving, since my lights would have been green at that point. I'd say there was a good chance that they also received a PCN in the post. That car was my only very brief obstruction to my last-minute decision to do a right turn - when I realised that my normal route back was closed off to me. AFAIK, I was not myself the cause of any obstruction to the only other traffic that was following behind me, since I had already made the turn by that point.
What the vid. doesn't show is that I pulled up on the pavement just a few feet further down to pick up my [registered disabled/Blue Badge Holder] wife outside Pizza Express. She's on crutches (post-op knee replacement), and cannot stand for more than a few minutes without considerable pain/discomfort. That was uppermost in my mind when I made the decision to ignore the signage. Enforcing the signage when major roadworks are in progress and no obstruction was caused looks a lot more like a revenue raising exercise to me rather than anything to do with traffic management, but I doubt that argument will cut any ice with them.
So when the deadline approaches, would appreciate some general advice/guidance about the grounds that should be mentioned in my reps, if you can spare the time.
Many thanks.