ModelRailroadForums.com is a free Model Railroad Discussion Forum and photo gallery. We cover all scales and sizes of model railroads. Online since 2002, it's one of the oldest and largest model railroad forums on the web. Whether you're a master model railroader or just getting started, you'll find something of interest here.
Contact Bob Brown, editor for Narrow Gauge Gazette, he'll be able to help you find a reputable brass man.....you could also try THE SHAY FIXER, just google him.
Whaty sort of repair? I know a couple of folks here in the US, but the shipping back & fortn across the border adds a layer of complexity and possibly cost.
I would suggest calling/emailing the outfits that sell brass. Uncle Dave's, or Caboose Hobbies, the manufacturers or importers themselves (Sunset, Division Point...). They have to fix items under warranty all the time.