AutoDesk simply won't respond positively because they just don't care about their customers at all. It takes at least 4 days for them to activate their software. On one occasion it took them a fortnight!
I don't know of any other company anywhere that charges around £3000 for a piece of software, takes your money and won't let you use it for 2 weeks.
There are only 2 ways to fix this, and only 1 is guaranteed to work.
The first is to complain in writing to Trading standards. I'm sure that by Autodesk knowingly modifying your software in such a way as to make it unusable has to be illegal.
Then write to the MD of AutoDesk UK and inform him of your problem and the actions you have taken. You might actually get a reply. Then I suggest you go and see your MP. You'll probably be fobbed off by being directed somewhere else like the DTI, but there is a vague chance that someone with a bit more influence will start to ask questions, particularly if you quote your meeting with your MP. Let's face it, if you were the director of a company doing this sort of thing, you wouldn't feel comfortable justifying questionable business practices to government, or a government body.
This is a lot of work, and will take up more of your time than you want. I don't think it will get a policy change, but it might well get you a 'official' workaround. It wouldn't do any harm to write about this to the MD of Apple UK.
The second solution is to start using something else. You probably really won't want to do this, but if you do, you need to get involved with it and shape it to your needs. It won't be able to replace your main tools now, but in time it might. I have done this. I moved away from AutoCAD, to Vectorworks and SketchUp, and years ago I got involved with development of an integrated render engine for the latter. I don't need AutoDesk products personally any more, and slowly I'm trying to move the office away. I know Blender has a complete b*tch of a UI and probably doesn't have loads of the features that you use, but it has been massively extended by hundreds of people all over the world, and it has some amazing modules for really complex simulations.
This is the only thing that will work. All powerful bodies (whether they are companies like IBM, governments or even the Roman Empire) eventually collapse because they get too lazy and lose focus. Even Microsoft are on the wane.
The obvious response to this may be something like, "What a huge amount of effort to deal with a truly shi***y company getting spectacularly rich by behaving in a truly shi***y way!" You shouldn't have to do this when you have legally paid for your hardware and software and invested an immense amount of time and money in it. For Autodesk to shaft you like this is utterly contemptible.
The fact is though, that if we just whinge about things like this but do nothing, nothing ever changes. I like this quote:-
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.
George Bernard Shaw (1856 - 1950), Man and Superman (1903) "Maxims for Revolutionists"
To paraphrase, I guess it's a case of what you are prepared to do about it. I genuinely don't mean to be be rude, but I think it's a case of "put up or shut up".