[Arran]

I just tried running the set off an isolation transformer and the noise was reduced just as much. Also, grounding the chassis has no effect.

I thought it did have an effect according to your last post? Maybe the isolation transformer has an electrostatic shield in it that would help?
Still I hate interference, all of this electronic junk (including computers and CFL) is not supposed to make RF noise and be FCC approved, of course that doesn't stop the Chinese from faking labels and getting it on the market anyhow.
Regards
Arran