So many points to follow up, I don't even know who to quote or where to start!
The 'centre lane owner driver' thing is definitely a major irritant, but I think motorway design can be partly to blame. I'm thinking of bits like J2 westbound of the M53, the East Lancs junction on the M57 (I forget the number) or J10 westbound on the M62 where the inside lane peels off at the junction. For the terminally clueless, the safest way to be sure to stay on the motorway is to avoid the inside lane, so that's what so many of them do.
I think the 'parks next to you in an empty car park' thing can be explained as people being unable to judge where the white lines are from inside the car. If they don't have a point of reference to park next to (i.e. another car) then they just can't get it right, so they take the easy option instead.
Like Scen1c, I can't stand the ignorant *******s who deliberately take up two spaces (to stop their car from being dinged or just out of sheer laziness.) I had a similar experience at the Holiday Inn in Dartford - someone had parked a Merc mostly in one space, but part way into the other. The car was in the end space, so it obviously wasn't the knock on effect of a badly parked car further along the row.' I managed to squeeze mine in next to it, so close that I had to retract the mirrors to get the car to fit. When I came down the next day, the other car had gone, so the driver must have had to climb in through the passenger door. I can only hope that he/she got the gear lever wedged somewhere nasty
And how about people who park in disabled and 'parent with child' spaces? In the case of the former, there's just no justification for it unless you have the badge. Prior to becoming a parent, I'd only ever use the latter reluctantly if no other parking was available. I've always accepted that disabled people and those with young children need the extra space to open the doors wide. Though I think part of the problem with 'parent & child' parking is that it invariably gets second priority to the disabled spaces, when it doesn't really need it, so some people park there just because it's nearest to the shop. I'd be happy to be tucked away in one corner of the car park, provided that the kiddie friendly supermarket trolleys were parked there too.
And fellow caravanners will know this one well: The complete cretins who park their cars in the caravan & trailer parking at motorway services, often leaving those of us who are towing with absolutely nowhere to park. Some services have started to put warning signs up, and I believe others are even clamping. I'd like to see that happen.