I am really suprised by some of the threads I've read, and I dont see why a borrowed neutral from 2 lighting circuit should be a big issue. As someone said, why should you ripped the property apart for one friggin neutral. Remember this is a fuse board change, as long as the load is corrected, a warning notice and its recorded, also, yes it can be a danger if this hasn't been adhered to. If borrowing a neutral from the socket for a light then I would have said its a NO NO.
Note: if you decide to run a neutral, never run one on its own, if I'm right as someone suggested.