Well then …… I've had to don my Columbo mac on this one. It's certainly out of the ordinary to what I see everyday, by way of network records.
On our bog-standard 'Network Records', it doesn't show Appleby has having any PCP's at all. However, with our on-line system (GEO-Hub), it does indeed show the Cabs you listed in your PM.
What it doesn't show though is the 'PS1' Cab that you are puzzled about, (me too now) ?? I've interrogated a number off the postcode for that PS1 Cab that you gave me, and the routing and records show the circuit to be going through PCP1 then SCP 1/5. I've personally never known there to be 5 secondary Cabs off the main one as suggested within that routing ?. The maximum I've witnessed is two.
The DP (Telegraph pole) for the circuit has a 'T' next to it and won't allow the usual further scrutinisation that would follow. It basically isn't recognised by our copper-based systems. So, all-in-all my guess, and that's all it is, is that there must be TPON.
Not much help I'm afraid.