Thanks, that's what I'm after, just certification to prove their competence. They're well versed in the operation of the items, but just wanted to know what they'd need to be able to connect power back to boxes etc. I think, from what I've read so far, that this NICEIC Safe Isolation course should cover it (as suggested by spinlondon). It's obviously all an exercise in keep us covered in the event of being queried by H&S/HSE. If any of the men aren't deemed competent then they're not touching anyway from the get-go.