The rules are simple and based on "safe zones"
You can only run a cable in a wall in a "safe zone" and a safe zone is either horizontally or vertically from any accessory, or within 150mm of the ceiling.
You cannot run cables at skirting board height, you cannot run them at an angle, only horizontal or verical.
Now, given most rooms have sockets on all walls and the normal socket height is 400mm above the floor, then you can run a whole bundle of cables around the rooms at socket height. So except in rooms that don't have sockets, that may be your route? there is aloways the within 150mm of the ceiling safe zone but personally I don't like that but it is legal.
I am wiring a house just now with some steel beams and there are just two 90mm holes in each steel, and it would appear the plumber has first choice at using the available holes, on the basis it doesn't matter so much if my cables have to take a longer route. But it is a PITA.