I found one today.
Homebase, about £8. Very faint buzz after connection, inaudible once screwed to the wall. Hooray. I only post this because I was the victim of an awfully buzzy one from B&Q this morning, and after googling the group I wondered if a quiet dimmer existed at all. It is unusual to find what you want in Homebase!
Al
All of them buzz to an extent..the worst being those that have crappo toroids in them for RFI..you can quiweten those by taking apart and smearing the windings with epoxy to lock them in place.
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