The HNC hasn't 'gone' anywhere, it is still widely availble at numerous colleges etc.
The current C&G offering in the design of electrical installations is the 2396.
Inspection and Test - City and Guilds 2396 Design and Verification of Electrical Installations Level 4
This regulation relies heavily on annexe Za of BS 60439 in order to be correct.
"Part 3 of the Standard, BS EN 60439-3, deals with the particular
requirements for low voltage switchgear and control gear
assemblies intended to be installed in places where unskilled
persons have access to...
Died a death when the 2360 morphed into the 2351 which was so poorly conceived it only lasted 1 year before being changed again to the current-ish, 2330
I think my year (97-00) were one of the last to sit the 2360 along with course c.
I do a lot of heating/BMS for a number of different manufacturers, myson included and as mentioned a screened beldon cable is the cable of choice. It comes in a multitude of different guises to suit any sort of power/switching application needed.