We've found it's varied. Mostly next to the tent. A couple of times half on the grass and half on the road. A couple of times away from the tent but were allowed to unload.
We actually prefer sites that dont allow cars to be parked next to the pitches.
Looking at nature or other tents is much nicer than looking at a chunk of metal imho but that is our preference.
We have never come across a site that doesnt allow cars on the pitches to set up/pack away. Carry a huge canvas tent from car to pitch? Erm let me think... no thanks :)
Seeing as most of our camping is at classic & custom car shows, er yes parking next to your car is allowed.
We're just back from a big show and how people were camping was shocking, cars everywhere and we won't mention the number of tents with guy ropes still tied up even in strong winds and people not obeying the 6 or 3 meter guidelines. Shame I didn't get any photos.
It's certainly a lovely spot, well off the road ie practically zero road noise. However on the downside, the facilities are a tad basic and the pitch sizes are a bit on the tight side.
Also, it is a working farm so you can expect to be woken early. All in all though, it's a really nice spot and as I said, a perfect base to explore a truly beautiful part of this country.