Baston
Glad to see you got the message on DR. The Navigation Manual (3456A?) gives you figures to work too. I also thought that I beat these figures "most of the time", but it is unreasonable to expect any crew to beat them "all of the time."
Now go back to my original scenario. You have shown at Aldergrove that the visibility is 3 nms and have seen nothing to suggest it has changed. You have the visibility you require to acquire the coast with a considerable safety margin. Why not transit at normal speed?
Remember the C130 example I gave.
Approaching the Mull I call "penetrate, penetrate go", the Captain will obey the script and abandon low level. However, once safely on the ground I will be asked to justify the call.
Can you imagine the reaction if I were to say. "Look, I know the vis was 3nms and we were flying in legal conditions, but I wasn,t very comfortable that close to the margins."
If I did that more than once the Squadron would quickly find a Navigator with more b*lls, and I would be flying a desk.