This is an interesting topic which has digressed from the original point to whether the "Y" cable family should be used or not. In an attempt to add to the debate here is my contribution, ( a little long but as brief as I can).
Part One of the Regs is a good place to start
Regulation 133.1.1 states:- "Every item of equipment shall comply with the appropriate British or Harmonized Standard. In the absence of such a standard, reference shall be made to the appropriate International (IEC) standard or the appropriate standard of another country"
Regulation 133.1.3 states: - "Where equipment to be used is not in accordance with Regulation 133.1.1 or is used outside the scope of its standard, the designer or other person responsible for specifying shall confirm that the equipment provides at least the same degree of safety as that afforded by compliance with the Regulations".
Regulation 133.5 (New materials and inventions) states that "Where the use of a new material or invention leads to departures from the Regulations, the resulting degree of safety of the installation shall be not less than that obtained by compliance with the Regulations. Such use is to be noted on the Electrical Installation Certificate specified in Part 6.
As Eland Cables state compliance with British and European performance test standards, these regulations basically allow its use and the designer (which could be the installer) needs to confirm on the certification documentation.
However as this type of cable has been manufactured for flexible control cables, designed for measurement and control in equipment careful consideration should be given before use as fixed installation power cables.
There has also been comments made about the braiding on this type of cable. Unlike SWA cables the braiding is for screening purposes only and should not be used as a CPC. Using the correct glands will ensure that this braiding is connected to earth. The cpc of this type of cable should be a core conductor coloured green and yellow.
Now going back to the original question by Lozarus regarding coding. Coding can be another big debate but I always ask myself two questions. Is there an immediate risk of electric shock (open live parts) if not it can not be code C1. Is there a risk of shock if a fault/failure occurs again if not it can be code C2 . That now leaves us with a code C3 to use.
Therefore I feel that use use of this type of cable can only be C3