Hello daveyjp, as far as I am aware there is only one Independent parking adjudicator system. My error for calling it a tribunal. All authorities, public or private, use the same process and same adjudicators throughout the country.

There are, for (bizarre) historic reasons, two appeal bodies for parking and other traffic matters enforced by local councils. One broadly deals with London, the other rest of England and Wales. Both are 'proper' tribunals, set up under specific laws and which came under the oversight of the former Council on Tribunals/Administrative Justice and Tribunals Council.

When the Protection of Freedoms Act outlawed clamping, but with quid pro quo of keeper liability appeals in that jurisdiction were initially 'sub-contracted' to the London tribunal using their systems and adjudicators. This was done under the auspices of the British Parking Association (BPA).

Since then two further changes have occurred. Firstly the BPA has re-tendered its appeals serviceand it's now run by The Ombudsman Service. A reputable provider which runs several other commercial dispute resolution services. But not a tribunal in sense of previous set up.

Secondly there has been a schism in the BPA and a rival trade body has been set up running its own appeals service.

While I've not seen any egregious decisions there are doubts about that body's real independence and the quality of it's (albeit legally qualified) adjudicators.

For those with an serious concern for the subject this piece by academic researcher Margaret Doyle may be of interest:

ukaji.org/2015/11/25/why-parking-on-private-land-i.../