@starrain
OMG I feel so much for you. These neighbours sound like a PITA!
Have there been any more developments? I would be worried that even if they are given a warning by someone (council/police/housebuilders,) that they will adhere to it for a while, and then just start slyly popping the car at the bottom again (half on the pavement/blocking you in.)
I am worried for you that this is a problem that won't go away until these neighbours move. I pray that they are in private let (some houses on these developments are,) and they leave within a year!
It's probably no consolation, but I (and my DH) feel your pain. Although we have not had such a bad issue as yours (being totally blocked in most days,) we have had issues in the house we live (on and off) for the 5 years we have lived here.
We have an astra, and we live at No 15, and the house opposite (No 14,) has 2 cars and a van, and a 2 car wide/2 car long driveway, that holds 4 cars. The man (Lee) owns the van, and the woman (Lucy,) owns a Peugeot, and the 19 y.o. son (Jack) owns a fiesta. As I say, it's a 4 car driveway, so the 2 cars AND the van easily fit on. But one vehicle will have to be behind the other 2 IYSWIM.
Last summer, Lee was popping in and out several times a day, and leaving the van on the road, half blocking our drive, so that Lucy and Jack could get out all right, during the day! He would leave it all evening and overnight through to mid morning sometimes, so Lucy and Jack could get off the drive without him having to move his van!
It became SUCH a nuisance, as it made it really hard for us to get in AND out of our drive, and when other people were parked on the road opposite too, it was extremely difficult to get out, and we kept scraping the tyres, and clipping the pavement. We had a few occasions when we just could not get out, and asked him to move the van so we could get out (then as soon as we drove off, he popped it back in exactly the same place,) so we struggled to get back into our drive later!
Upshot is, like your neighbour, they were doing everything they could to make life easy for themselves, and so they didn't have to keep moving vehicles to get in and out, and to hell with everyone else.
A couple lives in the house next to them (No 16,) and they frequently have visitors (and that house ALSO has a 4 car drive.) Yet the visitors are too bone idle to spend the 15 seconds it takes to park the car on the drive, and they often leave it DIRECTLY opposite our drive. Sometimes for half an hour, sometimes for 2 hours.
We have asked them time and again to move the car as we cannot get out, and they say 'oh sorry, yeah sure!' All nice and friendly, and then 2-3 days later, one of the fuckers blocks us in again. What pisses me off is that they have a four car drive, and still park on the road!
We have got to the point now, where, if we know we are going out later that day, we park on the road. At least we can be sure we will get out then! Funny thing is, when we DO park on the road, it makes it impossible for THEM to park in the place they want to park, and they have to park further down the road and walk an extra 30 yards (around 100 feet.)
And as they walk up the road, they glare at our car on the road like 'WTF have they parked THERE for?'
A few months back, I even heard one guy (visiting No 16,) say 'why is the astra parked there? Why are they not on their drive?!'
What a fucking cheek!
So it's OK for THEM to park wherever the fuck they want, making it awkward (and even impossible sometimes) for us to get our astra in or out, but it's a different story when WE park on the road. (And what's more, why don't they park on the FOUR car drive of the couple they're visiting opposite us?!)
We are never blocking the access to their drive, we just park on the road, NEAR our drive. But it stops them parking exactly where they want. Although, a few times, we have had van man Lee AND one of the people next door to him, park so badly/so close to ours, (when OUR car is on the road,) that the traffic struggles to get past.
If the road gets blocked (if a big vehicle needs to get past,) hell will freeze over before we move OUR car (if ours was there first, which is always is.)
The parking issues (for us,) don't affect us massively, and sometimes, we can go 3-4 weeks at a time without an issue, but if I am being honest, it is a bloody niggle. Especially with having to put the car on the road a few hours before we go out, just in case we can't get out later! 
God, I feel better for that rant.
Good luck OP, I am crossing my fingers for you.