If the fixed equipment is in zone 1 (although it could be zone 2) and can't be anywhere else then it's ok if on a 30ma RCD and IPX4 - flex outlet could go in zone 2 if IPX4 or in zone 3 - FCU outside bathroom
It's in the wiring regs - get him to read them
It may well need a rewire but can't tell without more detail - can you post pics of the CU and maybe the connections at the light fitting.
If the CU and wiring are very old then the safest thing is to replace all rather than bodge old and new - could have problems passing test results, need new...
The regs don't really help with this - I reckon put the full figure down - as long as the main cable is protected suitably by the fuse there isn't a problem. You are also meant to take into account any future growth in the installation so who knows where it ends!
Or if you want to you could...
I think Plug is right - I'd ditch the old junction box, use a rear entry box (or flush one into wall) and existing faceplate if in ok nick - a bit of a PITA position height wise though....could enter as near top as possible?
I would say 10mm as well - table 54H (from memory) in the regs has the spec
- unless you were supplied with a larger main earth I guess then it would be nearest half that size - 16mm is standard min in domestic(?)
Noticed this one on another forum:
”In a perfect world... spammers would get caught, go to jail, and share a cell with many men who have enlarged their penisses, taken Viagra and are looking for a new relationship.”
Is it BS 5266-1:2005 Emergency lighting. Code of practice for the emergency lighting of premises?
If so get it from http://www.bsi-global.com/Fire/Detection/bs5266.xalter
EDIT: First result from Google btw!!