CY cable is not true "flex" cable . Nothing wrong with it.
Well from the link I posted "CY cables come with a grey sheath, are highly flexible multi core cables with (class 5) copper conductors. They also have a voltage rating of 300/500v, having been manufactured to meet the requirements of BS6500 and VDE0250." it seems they are flexi.
Anyway we will have to agree to disagree. ..Clive