OK, so the good news, (if there is any !!), is that you have already paid all there is to pay, so by appealing the matter all the way, you could get all of that money back. You'll need to submit reps to Newham, and then. when rejected, register an appeal at London Tribunals, where your council reps will form your reps to London Tribunals. Your reps need to emphasise that the sign on Wednesday applied to the opposite side of the road, there was sign on your side when you parked that day.