Very interesting thread.
Here are the sentencing guidelines on this;
https://www.sentencingcouncil.org.uk/wp-content/uploads/MCSG-October-2018-FINAL.pdf
Page 152
Basically any speed over the limit is deemed an offence. In the 'older' days when stopped by an officer you could hopefully have a pleasant chat and get away with a warning. These days its all automated. The camera system actually triggers a Notice of Intended prosecution. (NIP). This is checked by a human and then posted. If a guilty plea is accepted by post then you may get offered a speed awareness course if the speed isnt too great. If not then your plea is accepted and dealt with under the single justice system. This is a single magistrate sitting in a room with a legal advisor going through the documents setting the penalty and the fine.
A Band A fine is half a weeks pay (deemed to be £120 if on benefits or £440 if not declared)
Ban B is your weekly pay, Band C is 1.5 x your weekly pay.
Remember also that the court can impose a discretionary disqualification for any single speeding offence. This is usually only for first time offenders who are hugely over the speed limit but worth remembering.
A guilty plea by post can be accepted by the court and then adjourned for sentencing if the offender is a 'totter'. That is they have 9 or more points already or the offence will attract enough points to reach 12 or more. In this case the offender is summoned to appear. This usually means the court is considering disqualification. If the offender doesn't appear they can be disqualified in their absence so they are warned not to drive on the day of the hearing. It has happened that an offender is banned in court in their absence. The ANPR system is updated immediately and they are caught within minutes of driving whilst disqualified!!!!
Remember also that should one plead 'Not guilty' and subsequently be found guilty at a trial, the costs rise from £85 to £620!
The cameras on the M4 and M25 are definately 'live'.