Good post from BM, Moggie. I've learnt something new today. I can't say I've ever come across the set-up you describe with the piece of wire ........ unless, as Zacs said, it's supplementary earth bonding.
I can comment on the TRV/roomstat set-up though. It's really worthwhile getting used to it. Simply, the roomstat sets the "global" temperature, while each TRV sets the "local" temp. that you're comfortable with in that area.
Much more efficient........... some rooms need to be kept at a decent higher temp. than others. TRVs let you "zone" your heating levels.