Yes, Trout Unlimited is an organization whose's " mission is to conserve, protect and restore North America's cold water fisheries and their watersheds". The Bitterroot chapter is a great organization of ladies and gentlemen dedicated to preserving the wonderful fishing found in your valley. They have monthly meetings and provide instruction, conservation projects and such. It's very inexpensive to join and membership will accelerate your learning curve tremendously.
Coincidentally, I'm off this morning to help my T.U. chapter work on a restoration project on the North Fork of the Salmon, the next valley to the south of you. Neighborhoods are quite large in the Big Sky.
This web site is a cornucopia of information and instruction regarding fly fishing and you're fortunate to have found it. I treat it as my morning newspaper and read through the posts every morning. I learn something every day. You'll also be delighted to see quite a few posts from England, Scotland, Whales and Northern Europe. The sister site, Spey Clave, ( click the icon at the top of the page ) will reconnect you to your U.K. heritage of two handed rod salmon fishing. Yanks call it Spey Fishing from it's namesake river in Scotland and it has become very popular in the U.S and Canada. You have two rivers in your neighborhood that have Salmon and sea run Steelhead Trout in them, the Salmon River, south on U.S. 93 and the Clearwater River, west on U.S. 12.
Good luck, Lance and I hope to run into you on the river someday.
Juro, you old coyote, it's been a long hard winter, eh. I wish you didn't live so far away. I could really use a tune up!