Ok so I went to an emergency call as the tenant had stated she was getting a shock from the shower. My employer doesn't really give much time for this kind of work, and doesn't pay OT, so arrived at 3.30. Carried out the normal tests on the shower circuit and found nothing wrong. Apparently this lady had had 3 shocks, the last one she said to herself I'd better be quick and carried on, lol
so I isolated the shower, and returned the next day.
all IR readings were good, well over 100M, except for upstairs lighting, which was incorrectly labelled as smoke detectors, the IR reading was .86m at 230v. Lighting was not Rcd protected, but shower, sockets and cooker were.
all circuits in the bathroom were bonded as per 16th
carried out a full EICR, and found the only one fault, the bathroom 16w 2d fitting was connected wrong, across L-E, I'm guessing that the shock was caused by the light fitting, passing current down the earth to the pipe work then on through the water and once the drains were wet, the lady got a small shock.
I reconnected the light, obviously, and did additional supp bonding in bathroom and to shower circuit,. The tenant hasn't had another shock since.