crb wrote:

BS7671 is not specific in this regard. It lists examples of
extraneous-conductive-parts that must be included, and also some that
need not be considered, but offers no definitive list or
characteristics.

But it does contain a definition, which includes the words "a part
liable to introduce a potential."

My view is that as these items will be isolated from earth and as there
is no foreseeable single fault condition or circumstance that would put
them at an electrical potential relative to earth (for all practical
purposes), then bonding is not necessary.

Agreed, on the assumption that they are fixed to dry insulating building
materials and not to, for example, any structural metalwork which may be
in contact with either earth or the main bonding.

--
Andy