The decision has to be yours. You can challenge it but it is likely to go all the way to a county court claim which you will have to defend. Depending on whether CE issue the claim themselves, which usually means they have a fairly solid case, or the hand it over to DCB Legal, in which case you are guaranteed that it will be discontinued if defended.
So, without knowing how they will proceed with it once the initial appeals are rejected (they will be), all I can advise is that should you feel that you have been issued the PCN unfairly, then if CE issue the claim themselves, you have a 50:50 prospect of winning. If they hand to to DCB Legal to issue the claim, then you have a 99.999% chance of winning.
The choice is yours. We will of course provide any necessary advice should you decide to fight the PCN.