The Emmanuel Brothers seem to have been around forever. Tommy played in loads of bands and as a session muso for years. Lots of pop music in the 80s featured brilliant guitar work from Tommy.
Might sound odd, but I've never heard his cds. He plays so much that he's pretty much everywhere, and I've never felt the need to get into his recordings. His acoustic guitar version of "Lady Madonna" is probably around 8 years old and quite well known. If you can find an album with that on it, it will probably be a good one.
I've never heard him play at folk festivals. He's pretty mainstream now - does lots of daytime tv appearances etc.
There are tons of brilliant musicians who probably aren't known outside of Australia, but how would we know whether they are or aren't?!