I was looking at the 550i clutch prices online a few months ago and there was a us based ebay seller selling them slightly cheaper than ECS yet there p&h fees were only like $40.
Have a look on
www.ebay.com
A clutch GB may be an option also, as whilst I dont need one I'm sure its only a matter of time (my car has 82k kays now, but alas most hwy kilometers so less wear on clutch components than a car which has 80k kays driving in the city)
I'm in two mind wether to get a cheapish and sensible 550i clutch, or if/when in future I get upgraded turbos I'll need something sturdier such as the spec 3 or motiv twin plate clutch...