Nothing wrong with cycling on the pavement, just how you do it that matters.
Unfortunately with no numberplates there is little point in reporting them.
Had a car written off recently by a driver with a fake numberplate, police can't do now't.
Your having a laugh if you think number plates on bikes will achieve more than the square root of zero.
The problem with the UK deficit is down to this attitude, everyone wants everything controlled/regulated or serviced by the government. The result is the government/police try to enforce or service all kinds of things that they can't effectively afford to do, rather than focus on a smaller number of items but do so effectively.
You just got to accept that some cyclists will be gits, all these calls for licences, number plates and tax won't do anything but make life more miserable, haemorrhage more money and not actually fix anything.
Saw a driver going the wrong way down a road the other day, and beeping pedestrains out of the way on a path/driveway entrance (clearly he had no right of way).
You think I called the police? pfffff, situations like that have to be dealt with by you and me.
See a cyclist going like a bell end on a path around pedestrians, do what I do, push him off his bike.
Ok, not everyone can do that, but stop deluding yourself that this is something the police will ever have the resources to deal with, or that they should waste their time doing so.