Need some help with a CPZ. What signs need to be in place for the CPZ to be valid?

Am I correct? Must every entrance to the CPZ should be signed on both sides of the road with a sign indicating that it is a CPZ and the times of restrictions?

Must every exit be signed on both sides of the road with a sign indicating that it is a CPZ and the times of restrictions??

Must any change to the times of restrictions within the CPZ need to be indicated with a sign where the change applies?

Thanks

A1. Yes except where you access the cpz from a one-way street, then only one sign is required.
A2.Yes, except if you are exiting onto a one-way street.
A3. Yes

Traffic orders or traffic management orders need to be looked at in these circumstances. They cut corners by altering the plates but it costs a lot more to alter the order so that does not change as a rule until there is more orders to amend to the original order.

Post the PCN and tell us the story.
Often better then asking questions that may not give the answer you need.

http://www.ticketfighter.co.uk/parking.htm#controlledzone

In any representation I would press them to the full to provide proof the signage was correct on the day in question.