Thats interesting, because im doing a rewire at my mums house next month and currently the supply comes up through the cavety and from consumer cables go up through cavety to loft (bungalow)
The property is about 40 years old maybe more, currently the consumer (old wylex) is fitted inside interior wall, behind you can see in cavety and exterior wall, bit windy shall we say!!
wondered myself if this is compliant these days?