Hi,
I'm over here in NZ. Have used AG spray method on several mirrors in the past. Larger sizes 22"-33". However due to complications in air freighting "liquids" (possible terrorist liquid bombs). I've decided to try out a local domestic mirror silvering firm. Been quoted NZ$40 for a 22" and $100 (GST inc) or a 25". I would insist on being there to "oversee" however. Maybe your best option would be to find such a service near you as I think it would make more economic sense.
Stephen.