1-4-?-2 (at idle..)

When idling my 2.25 petrol seems to have forgotten no.3 cylinder. I can unplug that HT lead with no effect to it. However at higher rpms (ie full choke) it starts working again and there is the expected drop in rpm when you unplug that HT lead.

I have swaped the HT lead and plug to cure the previous complete misfire - the plug has a good spark and i think the timing is ok as it runs a treat at any revs above idle.

Any ideas anyone? Its a mystery to me!

valve clearance tightened up or valve has hairline crack in it-listen for distinctive chuffing noise at idle and a compression test will prove it

Do a comp test, but first have a look at the dizzy cap very carefully on the inside for a crack, or track mark.
You can pull all the leads off, whizz the dizzy cap round 180 degrees, then put the leads back on and try it again, if the misfire is on a diffo cylinder then its deffo the cap.

check for air leaks on the inlet manifold
with the engine running spray somekind of carb cleaner around the gasket and pipes see if the revs pick up if so you got a leak

Cheers for that, il have a renewed inspection!