I bought a 12" f5 GSO mirror from Bintel a few years back (after some low-life stole all my gear, including my 10" dob that I ground myself).
The specs were better for the stand-alone mirror than for the one in the completed GSO scope (I can't remember offhand what they claimed, sorry: although claimed specs don't tell the full story).
It is a very good mirror and for way cheaper than if I ground it myself. Foucault testing shows text-book images for a well-corrected mirror. Star testing is pretty much spot-on, and high power viewing of Jupiter and Saturn show nice, crisp detail.
I don't know whether Bintel still source them: when I bought mine it was a "run-out" price as the last of their stock at that time. I think Matthew Lovell can source mirrors (
http://www.telescopes-astronomy.com.au)
If you want the high-end, guaranteed, hand figured stuff you probably need to check out Zambuto (
http://zambutomirrors.com/mirrors.html), Mike Lockwood (
http://www.loptics.com/info.html) or one of the other US makers (Galaxy?); I don't think anyone makes them commercially in Oz anymore.
Good luck,
Dean