Building the First of a New Type.
Your timing might be perfect to explore the new CAA "E" Conditions regulations.
These are specifically aimed at the encouragement of new designs without all of the attendant "Airworthiness" costs and complications.
http://www.caa.co.uk/docs/2907/20141...nsultation.pdf
I will be interested to see how you get on if you explore this route.
Good Luck.
Charlie