Car cam is a good idea, front and rear facing if possible.
The upshot is the Highway Code is the bible, but I'm waiting for the next release of Roadcraft to be released at the end of the month. That's the police drivers handbook and has some interesting guidelines in about staying in the lane you're in if you'll have to change again within a certain time, or if you'll cause the driver behind you to have to brake.
Picture this, you're driving at the posted limit and you pull out to overtake and do so, but if you pull back into lane 1 you'll have to pull out again within 20 seconds so you stay put. Lane hogging?
Or if you pull in you'll leave less than the guideline 2 second rule between you and the car behind? Which is more considerate, stay put and possible lane hogging or pull in and be inconsiderate (and possibly leave the driver behind open to a tailgating ticket)
The whole thing, while trying to address the right issues, is ill thought out, subjective and likely to snarl up the courts with people appealing.
The only possible upside is I hope the elephant racing HGV drivers will get nicked for lane hogging...