Woodsmith - 8' square - any larger and I think I'd be living in it...
Robin - the consumer unit for the whole house is in the garage. I was going to get whoever does the electrics,to run a feed from it to a separate small consumer unit in the garage.
I'm hoping that I can do a lot of the work myself, and then get the electrician to do the final hook up so I can get that all important part P certificate you need these days.