Yes your correct about the pilot when I referred to the BMS (Building Management System) that was what I was intending to say that a thermostat would be connected to it.
The old single phase colours red (live), black (neutral) and green and yellow (earth) were changed (except for earth which stayed the same) to be more 'harmonized' in the European countries. The old colours are not included in the new scheme , however extensions must be made from the old colours using the new colours. It was rather error prone in the beginning I'm told but has since become just another day on the job. Whenever you enter a spur or rose (JB or fixture box to us in the US) you must label the box notifying the electrician that new colours and old colours are present.
Example... there is not a heck of a lot of difference in how they wire in the IEC vs the USA it just that we have 120 volts and they have higher voltage around 230 volts for their line to neutral circuits. Their equivalent 12/2 g will have a brown and blue and bare wire or a green and yellow wire. Brown (hot), (blue) neutral or grounded leg and equipment ground (bare or green and yellow). They must color the blue wire brown in switch loops just as we color white wires black. So voltage is really where we differ. They have a much different way of doing things in the breaker panel which they call a consumer unit. The image below is a typical consumer unit with one gfci (orange toggle) protecting all the circuits. a gfci in Europe or the UK is called an RCD (residual current device). In the wiring diagram
the large center breaker is the rcd. Far right is the main breaker and the rest are of course the branch circuits.
And the wiring diagram inside a consumer unit and a typical cable just like our nm-b only 230 volts between brown (live) & blue (neutral) and a bare (earth).