...except that the UK officially recognises sealand as being UK territory, and UK law enforcement claims jurisdiction over the platform
so far nothing has been done on the platform that is a major breech of UK law, so they have not had to go out and enforce anything, however if you were to set up there purely to break the law then things could rapidly change.
if it's just copyright stuff that they ignore then it may well be ignored (just as it is in the rest of the UK), but the only protection from the law that platform has is the fact that it's not easy to get to so the police probably won't be bothered with most things (although if a large international cartel decided to pressure them about something...)
...someone at TPB didn't do their homework (although i guess they are banking on people not researching it properly in order to sell the platform and make a load of money from it...)
btw the platform is owned by the british government, who are the only ones who can sell it - however they have neglected it and not minded people moving in, but reserve the right to just turn up and take it back at any time, so you could pay all that money for a property in the UK and still not even own it
the opinions of the sealand occupants is not relevant to the subject of who owns it, what actually matters is the opinion of the country with lots of big guns pointed at it, and they have said that it is their platform. however it doesn't matter about the fact that the status is disputed, as any sovereign nation can invade any other at will and nobody can do anything about it (unless some other nation decides to do the same, and invade the invading nation...) so if the UK government wants to enforce its law on the platform, it is free to do so - either because the platform is theirs anyway, or because if it isn't then they can still take control of it and make it theirs
it is no different to me claiming my house as a sovereign nation and the government disagreeing and saying it is part of the UK, what really matters at the end of the day is that they have more guns and a bigger army
the platform has never been given any status as a sovereign nation, the only claims they have is a single court ruling where it was ruled that at the time they were outside of UK jurisdiction in international waters so UK law couldn't be enforced - the government later extended its jurisdiction and now includes the platform, so that old ruling about old territorial limits is no longer valid, very much like how certain countries used to allow 2 people having an argument to shoot and kill each other, the laws have now been changed, and trying to use an old ruling that it used to be legal as a defense would be stupid
the only real sovereign nations are ones with actual populations, making it kind of hard to try and just buy it - you could perhaps buy a dictatorship over a nation though but that would not really be ideal... you would have to buy/form your own army and overthrow a government and hope that the international community didn't intervene.
there are a lot of very rich companies who would love to be outside of the law, not just the mafia etc but even legitimate companies such as casinos etc would absolutely love their own island with no tax regulations to worry about, but they have to settle for temporary agreements for low taxes with small nation to get anywhere . although i'm sure there is a large casino owner that would love to buy the platform and set up a casino there - i bet it wouldn't take long for the british navy to turn up asking where their tax is