UKCPS PCN Help

Hi. I have read lots of these forums and seem to have got myself in a bit of a pickle of what to do next after having my appeal rejected.

I received a pcn for 'leaving the site' at the beginning of August and wrote back to UKCPS stating about the signage not displaying the site area, what proof they had etc of me leaving the site. Using the VCS v Ibbotson case as a guide.

NOT surprisingly the appeal was rejected and they have not quoted any reasons why. (obviously a standard letter)

I am struggling what to do next. They have told me that I can appeal via IAS
however it is well documented that this is a waste of time so wasnt going to bother doing that.

All the info I have read states about getting a POPLA code,however on the UKCPS letterhead it states that the are IPC and a member of BPA. The signage on site also states BPA.

This where I struggle can I write back to them for a POPLA code or or do I have to go via IAS?

Failing that I was just going to write back to them to tell them that their charges do not represent a genuine pre estimate of loss etc, that I wasnt going to pay their demand until they provide valid reasons why the ticket should stand and also that I would levy a charge on them for my time should they continue to pursue ie Court Standard £18ph.

Any advice would be appreciated. Thanks