Im a little confused, or probably just mis-informed. So there are two types of days you can get onto the track?
An organised track day and just an open road (so its used as a public road?). I take it the restrictions above are for just the open days?
Correct. You're not confused.
Touristfahren: turn up, buy ticket, drive on (provided you have insurance cover, which you probably don't)
Organised track days: book your day with a UK track day organiser, pay, turn up, do the normal track day thing and don't worry about insurance, or being on the track with Power Rangers, or lots of Dutch people.
Whichever you do, you will be responsible for the costs of any armco you hit if you have an off. If you come off in TF you'll also be billed for recovery, safety car, track closure time etc etc