On the subject of RCD's, I have one between my CU and Kitchen/Livingroom Ring Main Socket circuit.
When I switched OFF the B32 amp supply MCB (which is upstream of the RCD), to do an "R1 and R2 test", I was surprised that the RCD actually Tripped Out, the moment I connected my 16th edition tester, between the Earth and Phase Contacts, having placed a test link between the Earth and Red conductors in the consumer unit.
Has anyone encountered this, where the RCD trips, even though the Incoming Supply is OFF, during a course of an "R1 and R2 test"???