@Aprilx Parking,
The only rules which apply are those of the LA, with regard to on street parking, permits etc, paint on road, signs, even if someone chose to park in your disabled, marked space, your recourse would still be very limited indeed.
If a car is insured, taxed etc and road legal and restrictions do not say otherwise, you can park where you please, with no special regard to driveways at all, in a legal sense, under rule 243 of the highway code, you are not supposed to park near one, or near to a kerb which has been altered for access purposes, but there is no statute in law to prevent this. Even if someone parked on your drive itself, and was trespassing, your only recourse is in civil law there.
And to the original point, no one has any legal right whatsoever to park outside their house, nor to interfere even with someone blocking their "Drive" The law does however define a drive, and to cross a footpath without the drive being of adequate construction, is an offence in law incidentally. So it's as I stated, a free for all, given the regs as they stand, and the law.