what are the actual regulations for protecting cable

[dandt]

Sorry to ask.. ( I have tried to search for a definitive answer
This question is partly for specific projects but also for general advice and also to settle an argument with a mate) ..
anyway my old terrace house has/had a mixture of techniques
cable eg light switch just fixed to wall with clips
cable in plastic 'trunking'
cable in conduit under plaster
cable not in conduit buried in cement and plaster
cable going horizontally through walls with no sleeving
cable pulled through holes in joists
cable next to water pipes etc
With my own projects I try to protect cable as much as is possible given various restraints but what are the rules today..
Specific questions
1) does cable trhough brickwork have to be sleeved
2) when should metal covering be used (and would this stop someone drilling through or banging a nail through in any case
3) provided cable is in zone ie above or below socket, can it just be plastered over as is
4) is it ok to just clip cable to wall eg below a kitchen worktop (in plain sight someone is less likely to damage it accidentally
5) does horizontal to socket count as a safe zone
6) does the vertical zone above a lighting switch cover slightly off centre ie going along 'arcitrave' but not up corner of room
7) I'd better stop now!
I hope you get the general point of my questions. Obviously in a new build it is easier to lay cable perfectly, but I have an old terrace.
Thanks to anyone who can give straight forward answers. I tried to read (wade through) the regulations etc but failed to understand them

 

[skenk]

1) just insulated and sheathed, as far as i'm aware, space around cable should be filled to prevent the spread of fire
2) earthed metallic conduit or tough enough to protect against nails or screws should be used if cable not protected by rcd or more than 50mm deep, probably other reasons outside of domestic . . . to provide mechanical protection etc. Some metallic stuff won't protect against nails/screws, some will depends what it's made or and how thick. You'll struggle to get a masonry bit thru any metal.
3) yes but not best practice, although very common up here in the old buildings
4) if it's clipped in plain sight it doesn't have to be in a zone
5) yes
6) no it has to be directly above/below/left/right of an accessory or in a corner or at the top of a wall or it's not a zone.

mains voltage cables should be 50mm from pipes or extra low voltage cables or other services

you're only allowed to hole and notch joists in specific areas