Pezza
I don't profess to be an expert full stop .. but like so many of us classic bikers I do have quite a few hours "flying time" , I don't believe that plugs will signifigantly improve idle ~
NOW ~ in saying that I have just emerged from carb issues with my Trident and with two complete separate sets of carbs. I finally managed to get a reasonable stage one carb performance ~
( It would falter on stage one / 1/4 and idle was a real pain ~ )
Mine deteriorated to such a point the bike would not even run ~
Long story short ~
As I sent ALL my spare carbs and a complete gantry set to Brisbane to have bloke build me what I call a SUPER set of Amals I had no spares ! As I tracked the problem to #2 carb~
So a mate sent me a complete renovated carb and the bike instantly ran perfectly at ALL ranges!
We still have not worked out what is wrong with that one carb !!
I over hauled it so many times I can't recall ~
Now I can't say whether this is your problem but ~ suffice to say it may be worth the screwing around to get a spare carb and swap them around ! Or even replace what you have ~ Its a tiresome task but it gets like that !!