Well you were never allowed to touch the network's property (everything before and including the meter) but anything beyond that wasn't restricted. And it still isn't (in the sense that you can do anything as long as you follow the Building Control route).
Of course, you have always been responsible for anything you do (and liable for any mistakes) so if you do something dangerous you could find yourself in court - this hasn't changed either, but if you get it approved by Building Control you probably have quite a powerful defence if they pass something that later proved to be dangerous, but then this isn't America so the legal situation (being able to blame someone else) Is less important than doing things right in the first place, IMHO!
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