well, it got spooked.
a couple of weeks after i made the previous post, AC got less colder and then barely cold.
so, 3 weeks ago, i went to check and couldn't really find any leak anywhere, so i depressed the Low Side Port valve a tiny bit to see if it was still holding pressure (freon), and there was very little freon coming out.
This was a huge relief for me 'cos it shows that its not a Scroll Valve issue. If the System had held a lot of Freon and was still not cold, it would have pointed me in the direction of the Scroll Valve.
it showed the Freon had somehow either escaped God knows where or dried up one way or the other.
i filled it again with Freon (3 Cans) and its back to brrrr cold even when idle.
i've just bought this Leak Sealer and will put it in the System IF the Freon disappears mysteriously again, having used it in another car in the past and it worked great.