I quite accept and am happy that I have due notice of the highway code and fines or penalties that can be imposed under it.
Where is the due notice of a £130 fine imposed by a local authority?
Box junctions and certain other moves such as prohibited turns are enforced in same way as parking; they've been transferred to civil enforcement. That means that rather than being prosecuted by the Police or Traffic Wardens they're enforced by the Council via it's on street Civil Enforcement Officers or by cameras. The authority to do, in England and Wales, so is an order of the Minster for Transport under provisions in the Traffic Management Act 2004 - Part 6 and Schedule 8 and made on the application of the Local Authority. Scotland has its own legislation.
I think enforcement in London was rolled out prior to the 2004 Act under earlier. I was peripherally involved regarding the appeal and adjudication set up of the London scheme and it seems a bit more than ten years ago!!
A motorist aggrieved by the issue of a ticket for a box junction infringement has a right to appeal to the Traffic Penalty Tribunal (Parking and Traffic Appeals Service in London).
Not all LA's have taken the power to enforce moving traffic offences and some that do may have yet to bring it into effect. To that extent it's a lottery whether you get a civil penalty from the Council or a fixed penalty/notice of intended prosecution from the Police. Either can be avoided by following the rules.
In fact, judging by the Traffic Penalty Tribunal's website no English LA outside London is currently enforcing box junctions, though some in Wales are.