Has the judge been found to be acting outwith his authority?
Very difficult to answer that. In theory Judges have to follow rules and abide by the law. But, in practice, they are pretty much God in their own Court and can do as they see fit without repercussions. The principle behind this is to retain Judicial independance, but unfortunately, as we all know; power corrupts.
In any other business, a professional of this level making a mistake would have to face disciplinary action of some kind. Curiously this doesn't seem to happen with Judges. Even if they are later found to be wrong they are all but untouchable, and the worst they will face is a minor rebuke over G&Ts in the club.
I go with others on this; in the instant case the Judge has been ruled to have erred. This is neither the Claimant nor the Apellant's fault. So it is only logical that the organisation responsible for the Judge (The Lord Chancellor's Office IIRC) should pay the costs of an error by one of their own.
I would also argue strongly that if the Claimants were represented by a No Win No Fee firm, then the position is that they did not win and therefore the law firm should make good on its promise, and waive the fees.