It's completely illegal under our Constitution:
1688/9 Bill of Rights (which establishes Parliament, amongst other things, so they can't get rid of it), which restored recognition of our unalienable Human Rights as expressed via the Common Law, after the Glorious Revolution.
From:
Bill of Rights (c.2) - Statute Law Database
"That all Grants and Promises of Fines and Forfeitures of particular persons before Conviction are illegall and void."
Read it all, then read it again - you may be as gobsmacked as I was when I first read it.
There are at least two other areas that are significant with this regard, the first of which is Magna Carta:
"We will appoint as justices, constables, sheriffs, or other officials, only men that know the law of the realm and are minded to keep it well. "
and the most important, is failure to comply with those very concrete Constitutional requirements, puts our Monarch in breach of her Coronation Oath.
Which of course, is Treason as well as Malfeasance in Office.
Demand a refund.
eta: This is most important to grasp - PAY on the spot fines, THEN claim them back! If you don't pay and go to Court, then due process is carried out. If you make payment with no Court case, then they are in clear breach of the Constitution and MUST pay it back, with damages and costs, and should go to Court as defendants themselves (because acceptance of a payment for a fine prior to conviction, is concrete proof that promises and grants of fines and forfeitures, have actually been carried on - so they fall into a trap of their own making).