am I seeing a decrease in common sense
That is the main issue, I think, and it is quite general, in (private) flying and in other domains, in UK and everywhere. I am sure it is our own stupid fault to not have adapted aviation to the 21st century environment and mindset of smartphones and facebook. Even if only looking on from a distance, though, I cannot help thinking the loss of common sense and independent responsible thinking is especially dire in the UK.
That said: my own run-up checking is usually done during taxi, cutting one "magneto" then the other, and checking for the rpm drop to be obvious, and consistent between the two. Mind you, if the engine were running on three legs only or such. it would already have been obvious from the first instant. I particularly do not believe in the "into the wind" point, it has been in the theory books since Lilienthal's days but does it really make a difference? More important indeed to not disturb or annoy the nimby's, much less one's fellow aviators.