I hope they'll just be repaired, I'd imagine people won't keep doing it for that long, only at the moment because it's new. Eventually they'll become used to it.
Exactly, numberplate cameras are the best bet to manage this.
The people pulling them down aren't making some brave stand against surveillance, they're just arseholes annoyed they're now facing some consequences for the damage their out of date vehicles cause to other people.
The UK has one of the highest numbers of surveillance cameras per person, this is just a fact of life that people are used to. The ULEZ cameras are typically ANPR (Automatic Number Plate Recognition), the government already know what cars you own and how polluting they are. You can't deny that these low emission zones are decreasing air pollution and London needs it. The attacks on the cameras are because they are adding surveillance but because it is £12.50p per day if your car does not meet standards so is an added "tax" for living in London which is being forced on the local councils with little thought for the individual circumstance.
There is a Channel 4 show a while ago called Hunted which mimics the levels of surveillance the police have to track contestants down, it is both scary and interesting how much they can work out and track down.