I think there is power in all of the paddock but not sure. There's nothing to stop you parking in the back of the pit area apart from limited space - and it's noisier obviously!
Simon, as far as I'm aware the only mains power supplies are within the pit garages, pretty sure that there are no power supply points elsewhere in the paddock area for hookups. The other option perhaps if you have a generator is to park on the marshals camping area just before Tyrrells behind the paddock, if you get there early enough you can park close the entrance just behind the paddock and close to the water supply! It's normally a bit quieter there.
But if you want to be close to the action and benefit from a power supply parking up behind the pit garages would be the best option.
Terry