maxstrammer - I don't know whether you're still out there but - if you are - I have a couple of thoughts on your parking issue. I'm not a lawyer but I understand that you can acquire a prescriptive right to more than just access. If you have parked for the twenty year period, openly (which it sounds like) and without using force (which it also sounds like) and without an agreement to do so with the Council, I would have thought you had acquired the right to continue doing so. The key seems to be whether there was any "agreement" with the Council. Presumably there was no parking ticket - even if free - and if there was no notice up, saying that the Council owned the site but agreed to it being used for parking, it would be difficult for them to claim that you, and others, parked there by virtue of an agreement. The three requirements, that you parked without secrecy, without force and without agreement would seem to be have met.
My suggestion - if you're still there - would be to write to the Council, stating that you have parked there for twenty years, openly and without anybody (the Council) challenging you or preventing you, and that you are willing and able to make a statutory declaration to that effect, and that you have acquired the right to do so in future.
The Council ain't going to like it - especially if it could apply to many other people - but the advantage of dealing with public organisations is that, if you ask clear and accurate questions, they do have to respond; in this case telling you why your claim is not accepted or at least saying something.
If you're still out there, give it a whirl - and good luck!