I don't "know" them either but I wanted to give an alternative to the I.O.V. and I know that there are a few suchlike organisations. I must be honest and say that I find the use of the word "guild" a bit pompous, especially as it took me a long time to get into my particular "guild" but I digress..
Ahh, my error, I mistook them for the APV (
www.apv.org.uk ) anyway there are shedloads of wedding videographers clubs/guilds/associations out there and most of them have licencing schemes for music.