You do not say what sort of generator you are sourcing, wind, water or other. You really need to talk to an experienced installer, who is used to dealing with the electrical distribution company. You do not say who your distribution company is. The problem with higher output generators, i.e. those exceeding the G83 limits is that they can overload the local distribution network. I had to have my transformer 'tapped down' to accept a 6kw output, single phase on G83 authorisation, at my expense. usually this is only a problem if the transformer, from the 11000volt distribution to your house (or a group of houses) has been 'tapped up' well above 240 volts, particularly if it is up at 253 volts, when it does not allow enough 'room' for the generator to feed in withoutgoing above 260 volts when there has to be an overvoltage disconnection from the mains.

If anyone asks me how to get started with installing a grid tied generator, I will say first talk to an experienced installer an the power distribution company. If you let us know where you are, I am sure that someone will be able to advise on a good local installer.
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Simonridout