I recently (a few weeks ago) watched "Tess of the D'Ubervilles" from A&E/BBC, and there were quite a few concertinas shown.....along a cameo appearance of a serpent!
Several of the characters (background musicians) played Anglos, but the hero played an English--I just KNEW he was a good guy! The dubbing was rather painful though. Not quite as bad as I've seen before, but close. Apparently the concertina is easier to appear to play than the violin is.
Yes, Gaelic Storm was in the Titanic.....I've never seen that movie, but I have been to see the band a few times. Oh my gosh--the musical equivalent of caffeine, let me tell you.
Probably the Mellstock Band with Dave Townsend plating English concertina.
(they certainly have a serpent :-)