Hey Maxey-
This UK supplier comes very highly recommended, and their bulbs just won some accolades as the best value in 2005. They are also offering a hard-to-beat 2-pairs for price of 1 (not sure how long it'll last)
Check em out at: http://www.powerbulbs.co.uk.
I can't link directly to the X5 bulbs, but there's a vehicle search on the page.
I'm ordering their fogs so that they'll be a closer match my Xenons once my conversion is done.
Good luck.