Location! Location! Location!
Nobody else has mentioned it yet, so I feel like it's safe to bring up the subject:
Didn't New Zealand provide wonderful locations for the shooting of the film, doubling for Edwardian England like that?
You'd be hard-pressed to find suitable locations in the UK that matched the landscapes of a century ago, where you didn't have to digitally remove anachronistic evidence of the 21st century - in New Zealand, as Peter Jackson found, there are enough wide open spaces to film without seeing so much as a telephone pole, or even a road!
Brilliant idea to shoot there!
(Also, handy for Bryan Brown & Sam Neill, who live around Sydney, Australia - 3 hour plane trip and they're there!)