I play in an old-time Appalacian band called East Creek Union. We've played at Red Rooster, the sadly defunct Orwell Bluegrass festival and Folk East. This year we're doing Maverick. Red Rooster in particular has a very wide ranging definition of "Americana" encompassing old-time, bluegrass, country, blues, rockablilly, new orleans style street jazz, country rock and people like Pokey Lafarge who dont' really fit into any category.
I like going to Red Rooster, I hear a lot of acts there I wouldn't otherwise come across.
The UK America Music Association who I believe are invoved in booking acts for Red Rooster and maybe other festivals too. We certainly can't get a sniff despite having played there in the past. They have slots at certain events for members to apply. I was thinking about joining, but I don't like the T's and C's which require you to sign up to a Continuous Payment Authoritty (CPA), I'm not keen on that idea.