Well emboldened by Doug's comment I've just given it another go. I checked No 1 with copper grease on the seat area to see if it seated - which it does.
Then again on No 2 and it didn't. So I tried oiling the thread and running it in an out a few times, each time seeing if it seated (it didnt). So I carried on turning for a bit longer and it did tighten. So I pulled it out and put it back again and it tightened better. Still not a satisfying "nipping up" instant tightness, but it is more torqued than before.
Good thought John - I have the old plugs so I could try one of those back in again.
I am more content now though!
Nick
