I think the above explanation (which I don't dispute for a moment) demonstrates what a mess the rules are.
FWIW, in days before I had any understanding of this (nobody told me during my UK PPL/night training that night=IFR) I have departed from major UK airports, asking for a "VFR departure to XXX" and nobody said a word. Either ATC didn't know the rules either, or they knew them and were just being kind.
I think that if you lined up 100 UK instructors and asked them about ANO article 26 or whatever, 90 of them would say they have never heard of it.
My experience of hanging around the flying scene for a few years is that almost nobody has any understanding of these rules. People just go and fly. Those with a plain PPL+night know they are supposed to keep out of cloud, and those with an IMCR/IR know they don't have to.
Same with the stuff about the 3000ft transition altitude. In practice nobody in the ATC world seems to give a damn about this 3000ft figure, day or night. Occassionally, when getting an RIS, one is asked to adjust from 5000ft to FL050. And, when OCAS, you can be non-radio so it matters even less where you are.