gdev2009
You've already been told where to look for the information you need.
Click on 'Join Us' and you'll find the Secretary's postal address and e-mail address. The Secretary is Jeremy James.
I've got his phone number but I don't think it would be appropriate to pass it on. If he'd wanted it widely known he would have published it on the website.
He clearly wants contact to be by post or email.
I'm not a member of the HCGB so cant help further.