Martin Bonner wrote:

OK. That's why I wanted a professional.

You didn't get one though...

In fact the regs generally forbid inserting switching devices in
protective (earth) conductors, for fairly obvious reasons.

Having checked, there is an exception allowed in the new edition for
this and earth switching is allowed where essential, subject to various
conditions [see 537.1.5 for details].

Oh sure. I wasn't saying anything about a switch! I just thought
that they company earth was permanently disconnected. Presumably, it
would be /allowed/ to disconnect the company earth, but a silly thing
to do (why disconnect a perfectly good earth).

There's no compulsion to use a supplier's earth facility, either TN-S or
TN-C-S/PME. The TT option is always open, but of course conversion
would usually involve fitting at least one additional RCD. I don't see
any need or point in doing it though, if there's a good TN earth
available, unless the supplier or distributor imposes it as a condition
of having a generator.

--
Andy