Large format film is certainly getting more difficult to get in Canada. Kodak is no longer supplying 8x10 and larger film through Kodak Canada - the local camera store (named, suprisingly enough, The Camera Store) has been flat out told by the Kodak rep that they will NOT supply 8x10 film in Canada, regardless of the order size. 5x7 I think they must purchase by the case. 4x5 is still available, for now.
That said, the prices that are offered in Canada are better than what you can get in the US, at least for Kodak 4x5 films. A 50 sheet box of Tri-x is about $55 Cdn, whereas in the US it's around $56 Cdn. Not sure about Ilford, I don't use their films.
And Deniz, I'm with you on the Custom's fees. They *suck*, and are just another price gouge. If you can swing it, try and have things sent via USPS - at least this way, you'll pay a $5 handling fee + GST (via Canada Post), which is still annoying, but certainly less than what you would pay using a courier company.
I would also mention that I believe the GST is included in the brokerage fees, so perhaps the fees aren't as bad as you thought?