Thanks, Nigel - is there a "not" missing somewhere???! Looking back at the wiring diagram I posted, I THINK that where it says "Distributor 230V" this will be Panel 302, confirming what Mark_C says about being able to remove the isolator keys but keeping the RCD switch on panel 302 in the On position. I'm hoping to pop up to Freebird tomorrow to do just that (and to look in at Bavaria Fest in Largs on Saturday!)