That makes sense, and considering you mentioned they have been there since 2006 and they still work, shows maybe its not such an extreme environment....
Something else you might want to look at, the wiring in the trunking, when you open the trunking in some places they full of oil, if so are the wires...
Another motivation for fitting an earth leakage is that those particular socket outlets do not appear in 6.7.5.5 as one of those not requiring earth...
On point 1) The wires from the lights were not connected in the draw box. The red and black wire going to the light was connected to the switch with...