Returning to my question - is it a crime against BS7671 to omit the isolator altogether?

Not a crime, but maybe takes a bit more to achieve a similar level of safety and convenience using the CU. Single pole MCB for isolation? Certainly not on a TT system and probably not on a TN system if its downstream of an RCCB (or accidental touching of N-PE risks tripping the RCD and taking out other circuits), The CU is probably remote from the equipment to be isolated - so the means of isolation will need to be able to be secured - how many plumbers or DIYers are likely to carry lock out kits for all the various brands of MCBs/CUs?  And it's simpler and easier to pick the correct isolating device if it's right next to the equipment.  Maybe more of a design challenge that simple BS 7671 compliance - but if a compliant solution is in some ways less conveniently safe than 'the norm' - is it really acceptable?

Maybe it's just that the accessory standards need  bit of improvement....

   - Andy.

Returning to my question - is it a crime against BS7671 to omit the isolator altogether?

Not a crime, but maybe takes a bit more to achieve a similar level of safety and convenience using the CU. Single pole MCB for isolation? Certainly not on a TT system and probably not on a TN system if its downstream of an RCCB (or accidental touching of N-PE risks tripping the RCD and taking out other circuits), The CU is probably remote from the equipment to be isolated - so the means of isolation will need to be able to be secured - how many plumbers or DIYers are likely to carry lock out kits for all the various brands of MCBs/CUs?  And it's simpler and easier to pick the correct isolating device if it's right next to the equipment.  Maybe more of a design challenge that simple BS 7671 compliance - but if a compliant solution is in some ways less conveniently safe than 'the norm' - is it really acceptable?

Maybe it's just that the accessory standards need  bit of improvement....

   - Andy.

Good point about the risk of losing one half of a duel rcd board in the event of a dead neutral and cpc coming together at the shower end.

The actual isolator took some finding, it being sited low down and behind a heavy wardrobe on the wall dividing the bathroom from the bedroom!

This is not uncommon, with cooker isolators buried in kitchen cupboards behind jars and plates, or not even fitted at all.

In terms of improved accessory quality? I would say that this is well beyond our scope of control as installers. You can only tiddle with the willy you've been given!

Maybe this is where the various doyens of the BS7671 committees should be directing their ire. A new resolution is required. "The committees JPLE64/BS7671/IEC et al shall cease the practice of treating symptoms and instead shall focus upon detecting and remedying root causes".