That's weird! After I posted, by way of a last throw of the dice, I took the plugs out (again) turned the engine over a few times then put some new plugs in. It started first try and ran perfectly, as with you cskip. I dont understand this as it had been running perfectly on the old plugs before I started fiddling.Pehaps it was flooded?
I'll get it hot then try the old plugs and see what happens.