Clearly the council considered that a repeater sign was needed at this location, and rightly so, because they have only put up a single sign at the entrance to the street. There are a lot of these restrictions around these days so one must be on the lookout at all times. As the sign is missing, one could argue that the signage is inadequate in its current state.
The test here, to win at adjudication, is the question - "is the signage adequate to convey the restriction ? " The council will never give way, because they keep the money if you cough-up, so they will refuse all your reps, both informal challenge and formal representations.
The problem with "adequate", is it is subjective, your "inadequate", is their "adequate", and the only unbiased view is that of an adjudicator at the Traffic Penalty Tribunal. This means you'd have to risk the full PCN penalty, there is no discount at the adjudicators.
Adequacy of signage is their duty in Regulation 18 of the The Local Authorities’ Traffic Orders (Procedure) (England and Wales) Regulations 1996
https://www.legislation.gov.uk/uksi/1996/2489/regulation/18I think you have a case on the grounds of inadequacy of signage, and the repeater sign was there once and is no longer there. So submit an informal challenge on this basis, but expect to get a Fob-Off letter. Post their response when you get it, as they may shoot themselves in the foot. The point is that the council posted signage on the implementation of the scheme that they considered adequate. But now it no longer is. As well as this, the existing sign at t he entrance to the parking for a group of terraced houses in a cul-de-sac misleads because if you miss the street entrance sign, this sign misleads you into thinking parking is allowed on the rest of the street. It is the usual Dog's Breakfast we see so often on this forum.
