If you now want to test the matter at London Tribunals you must now register an appeal with them. There is no need for your final appeal text to go in at that stage, you should just say "I rely on my formal representations to the council", (I'm assuming you mentioned the lack of advance warning and obscuration of the signs as per your photo). Of course you'll be risking the full PCN penalty, but that is all, there are no other costs or charges, and if you win, you pay nothing. From what I can see, the council have just stated what happened and haven't addressed any points you made in your reps, so you could emphasise this in your appeal, (it's called "failure to consider").