The TSRGD diagram (1028.4) for this type of bay carries a road marking, 'DOCTOR'.
'1.—(1) ”DOCTOR” may be omitted.
(2) “DOCTOR” may be varied to: “BUSES”, “CAR CLUB”, “CYCLE HIRE”, “DISABLED”, “ELECTRIC VEHICLES”, “ELECTRIC VEHS”, “ELECTRIC MOTORCYCLES”, “ELECTRIC M/CYCLES”, “ELECTRIC M/Cs”, “LOADING”, “LARGE OR SLOW VEHICLES”, “PERMIT HOLDERS”, “SOLO MOTORCYCLES”, “SOLO M/CYCLES”, “SOLO M/CS”.'
So 'DISABLED' is a valid variation but only when the restriction applies to disabled persons.
In this case it does not. IMO, the cited decision bolsters the OP's argument.
LATOR requires by inference if not stated in words that any 'traffic signs' (and a marking is a traffic sign) must be lawful and compatible.
IMO, the combination here is not. We have the adjudicator determining that these bays are permit bays. Therefore the council must justify using an unlawful combination of traffic signs. (and if the marking did apply, the bay's still wrong because it doesn't meet the min. width criterion)
One for cp, as regards the road marking, surely if a BB holder sees this and knows that they are not in any of the exempt boroughs then they may presume a minimum of 3 hours' parking on display of a BB and clock without needing to look for a traffic sign?
OP, for other comments.