So essentially, you're arguing about adequacy of signage. However the council will argue it is totally adequate, so will refuse your representations. All the regulations say is that the council must erect sufficient and adequate signage to convey the restriction to motorists. "Sufficient", and "adequate" are subjective, so the only unbiased forum open to you is to take them to London Tribunals, (the adjudicators) and argue your case. The council will also argue theirs, and the ajudicator will make a binding decision. To do this, you must risk the full pCN penalty.