I only get the vibrations when braking (hard) from high speeds. I suspect it's because the rust was (hopefully was, anyway) half-removed on the rotors and the pads were gripping on the patches of rust left on the discs then sliding on the smooth parts. I can't see why the rotors would warp - I haven't exposed them to sufficient heat/quenching for this to happen.

I accept I drive spiritedly but hopefully not like a complete nutter!