Amidst much gnashing of teeth I've discovered I forgot to attach bonding
clamps to the shower (a) before I tiled it and then (b) before the
plasterer came at the weekend to skim the rest of the bathroom. OMG.
Shower valve is fed by copper pipes from above in the roof space, so I
have no option but to apply earth clamps up there, and drop the cable
down the cavity wall and bugger up all the new plaster to get through
the noggins; thereby to connect up to the other pipework which comes up
from the bathroom floor (don't ask - previous occupier had it plumbed
this way!)

Anyway... rant over - main question: do I have to bond shower - sink -
bath - towel rail all with one continuous cable (which is what I always
do), or is that just good practice? ISTR reading somewhere that it was
mandatory but can't find anything about it now, and it will be a royal
PITA if I need to.

Secondarily - I'll bond the H&C pipes at the sink; but if I also have a
metal shower bar fed by copper pipes (no plastic anywhere in this
bathroom), do I really need to bond the H and C pipes to that as well?
Doesn't the shower valve act as conductor (or could, eg, PTFE tape in
the fittings potentially act as insulator? Indeed; do both the H&C
pipes feeding the plastic bath also really need to be bonded, given that
they will already be connected by copper pipe under the floor, by virtue
of the sink bonding?

(These are all things I'd normally do, by the way; I'm just wondering if
it's overkill on my part!)

Thanks
David