Sadly I don't have the time, but I like the idea of setting up a group to develop a UK amateur helicopter. I'm personally quite comfortable from my own experience that it can be done safely - in fact in the UK you'd struggle to be allowe to do otherwise unless you completely ignore the existing rulebooks for amateur development.
But making money I think is optimistic - do it for the challenge, kudos and satisfaction - in the unlikely event you make any money from developing a light helicopter, I'd regard that as a huge and unexpected bonus.
Mind you, the same is probably true of most other aircraft design projects - it's not a peculiarity of helicopters.
G