Seems that the law is a complete ass. "it is the responsibility of each local authority to determine whether any additional charges are to be levied." That basically gives them carte blanche to charge whatever they damn well like!
No, the law isn't a complete ass, the law (in this case) is open to different interpretations as rehearsed previously.
Any civil servant, local government officer or, indeed, employee of a private company can and will only interpret the law with the aim of ensuring that the organisation they work for is operating legally. No civil servant or local government officer can state, definitively, whether or not another public body is acting legally. Even a law enforcement officer undertaking a prosecution of someone only states that he thinks the person/body is acting illegally.
The reason is that only the courts can rule definitely - and, even then, the rulings of lower courts can be appealed at higher courts.
The GRO has stated that local authorities must satisfy themselves as to whether they are acting legally and Salford Council has stated that it has done so.
It would be possible to use the Salford Council complaints procedure to have that stance examined but I should have thought it unlikely that the internal stages would result in it being overturned. A final appeal could then be lodged with the Local Government Ombudsman but the likelihood is that the LGO could not order Salford to change its mind even if the LGO found against the council.
The only other option, and the only one which can produce a definitive answer, is to take Salford Council to court.
Graham