I've just done this on my E71 after changing the air bags. I have access to dealer level gear but I would have thought any indy could do the job. Only takes a few minutes.

Check the banjo bolt and oil feed lines are completely clear.

Not the right section of the forum I know but my x6m does between 10 and 25 mpg

Mine had the nasty habit of re-engaging even when it was off

Sounds like a system leak. Any good air con company should be able to put fluorescent dye into the system to find any problems before putting expensive gas back in

Mine used to randomly drop or stay up for days. Problem is if it has a slow leak then the pump will be running a lot and it's not really designed for that.
As for changing one or both, if one has a leak and they are both the same age, then I would doubt the second one will be far behind in failing....

Only the wheel centring ring itself is supposed to have any lubrication. The official instructions are that the mating surfaces should be cleaned to ensure no dirt, grease or debris lies between the surfaces. BMW even have a special tool to ensure this is done - they would wouldn’t they I agree, ...

Continuing on my post about BMW workmanship being abysmal, if you have your car serviced by a main dealer, don't think they do a proper job. You would think that part of the servicing would be putting stuff back with lubricant or grease as required. To me part of that would be refitting wheels with ...

Well, battery drain turned out to be a damaged charge air coolant pump. Had the be the hard one to get to. And continued to find missing fasteners, unclipped pipes and so on. Really must have had the apprentice on this car.
If any one has a problem like this it came up as a LIN wire fault

4.8 V8 according to tax check

I agree, an air bag seems to have popped, assuming one of the air pipes isn't damaged.
I've just done this job on my X6 and it is very straightforward took me about 1.5 hours but I did have access to a car lift.
I fitted Arnott bags, not genuine bmw.

A lot of problems with the emissions systems are also caused by failure of the myriad sensors. This will prevent the dpf regeneration cycle and if you leave it long enough it's turbo time. (Or two..) And take a look inside the intake manifolds if you get a chance and see what egr recirculation does ...

Pistonheads or ebay

Modern diesels are a fantastic pieces of kit and usually very reliable. The emissions equipment are neither and will give you problems if you do lots of short journeys. And it will be expensive.

Regarding the charge costs, the question in my head is are the charges you pay at home a reasonable charge for the power used, or is it being subsidised by other consumers?