The oddly named APPGOPO has been going for over a year now, and regularly has open events where speakers are invited to give presentations on relevant topics, with a question and answer session afterwards.

http://www.appgopo.org.uk/

I went to the talk last month on ultra-low carbon farming, with some interesting points raised (The presentations were recorded and are posted on the site linked above)

Next week, the event is "The Global Impact of Peak Oil: International Relations & Business" which I shall also be attending. I'll let you know if there's anything of interest raised.

Feel free to sign up to the group to get updates and invitations to future events.