4 wire (including pilot) Electric Heaters - Relocating?

[Scarletpimpofnel]

Consider a flat that has it's electric heaters controlled from a central Dimplex controller using 4 wire cable that includes a pilot wire. Sadly all the heaters are in awkward places (where the curtains hang, where the bed head must go, where the settee goes etc) so all need moving.

If you consider there is a flat above and below, where are the cables likely to go? Will they run down the wall then behind the skirting or horizontally between heaters? I don't mind wiring but wish I had a good idea where this type of cable is likely to run.

I am wondering if the easiest thing is to simply extend the current wiring using surface mount trunking as an easier way of extending the cabling than trying to locate it in the walls and fish it through to the new locations? Any thoughts on best way of finding/extending this cabling?

Thanks