Around Manchester I can't remember the last time i DIDN'T see a cop on the motorway. The stretch near my house there are always two parked up. The middle lane rule is going to be very subjective and hard to enforce I think.
BTW, these two fine-able offences are complete bollocks.
Overtaking and pushing into a queue of traffic
Being in the wrong lane and pushing into a queue on a roundabout
There's nothing wrong with overtaking as long as you've not an idiot about it. And being in the wrong lane happens, we're all done it, the problem is dicks not letting you in.