I'm a member through my club, not sure what extra I'd get with full membership? I get Summit anyway as I advertise in it.
Obvs lots of ways to try and boost membership. The website not being responsive nor even having a mobile version can't help. I'd expect at least a third of traffic should be from mobile but seeing as the site is unusable...
Summit is fab and the BMCs social media communications are excellent but when it comes to the means of actually taking out membership, there's way too much "friction".