I tend to buy all over the place, depending on prices. Craig Hunter is a good guy in Victoria for sure. ebay.co.uk is a bit of a crapshoot, but I've had pretty good luck with some things, particularly from minimine-ltd (they're a spares supplier from Stoke-on-Trent). Shipping over isn't too bad if the part is small enough to go Royal Mail Small Packets.
Have gotten a few good used parts (e.g. front subbie) for decent prices from a guy named Rudy in Toronto. He advertises on kijiji.ca and at the Vancouver Mini Club want ads. Looks like he's mostly a breaker, but the parts I've gotten have been clean and in good shape. He also ships Greyhound Courier in Canada, which is cheap and pretty quick if you have a Greyhound depot nearby. His photos of Minis cut in half and so forth are heartbreaking however!
There's a surprising (to me) number of listed Mini parts on The Ka-jeeg (www.kijiji.ca) here in Ontario at times...at your own risk, of course.
Edited by zinzan, 22 September 2012 - 12:21 AM.