This is a tough one. I checked out forums around solar energy and stuff like that, and ones like this look promising: http://www.solarguide.co.uk/forum/
I guess it depends what kind of help you need. If it's simply advice, then I'd give the site above a try.
There is also a DIY category on Meetup.com (http://diy.meetup.com/) which could be useful for finding DIY enthusiasts to meet up with. None seem to be solar energy speciic though.
In fact, most are quite heavily tech-orientated. But it might be worth a browse anyway!
