Hi Iain. Welcome to the Fanatics!
Well your post is certainly interesting, mostly cause I'm from Greater Vancouver too. You're the first local besides myself I've seen posting.
I'm guessing the store you're talking about is Imperial Hobbies? I don't know of any others carrying Mantic stock instore. It's a great store, one of my favourites, but they are a bit cramped for gaming space. Have you ever been out to Gamestars in Langley? I've spoken with them and they are open to Kings of War Demo games. I haven't done it myself yet for two reasons.
1/ I've never had an opponent.
2/Despite being a Mantic Fanatic/customer for almost 3 years now... I've never actually played a game. I'm mostly a painter/collector these days and even that, as gaarew will be only too eager to tell you, I do VERY slowly. So far, I only have some of my Elven units painted up and am part way through my Dwarfs.
Anyway, once the new rules come out, I'd be interested in learning them. If you're into it, we could meet up at one of the stores.
As for active forums for Mantic, you should visit the official one.
http://forum.manticblog.com/forum.phpit's also a very friendly place. The only thing is, once you register there, it requires an Admin to approve you before you can post. From past experience, that might not happen over the weekend but give it a try anyway.