Dave Plowman wrote:

I'd have thought if you need earth bonding on a system which has copper
pipes, the bonding should go on the rad - not the pipes. If the TRVs etc
have any form of gunge between them the pipes and the rad, this could
introduce electrical resistance.

Hmm, interesting thought. All of the bonded setups I've looked at (in my
capacity as a nosy visitor in other people's houses) have had the clamps
on the pipes near the radiator, not on the radiator itself. I've often
wondered about the electrical usefulness of this.

--
Grunff