Looks like ive found the problem,whilst looking at new coil packs I saw that the rubber plug covers detach from the pack so I pulled mine off & found no.4 ht post completly covered in rust(from having a cracked head & coolant filling the plug hole,temp fixed with holts+).
The rubber cover is very good at keeping water around the post once it is wet.
Cleaned the post,is nice a shiny now but a bit pitted from the rust,also cleaned the double spring from inside the plug cover,put it all back together & this fixed 80% of the problem.
Had to risk changing the plugs & making the crack in the head worse.
I can see why the head cracked,no.4 plug was so much tighter than the other plugs.
Changing the plugs has seemed to fix the rest of the problem so far.
I'm waiting to see if changing the plugs has opened up the crack again!
Could the constant missfireing have damaged the plugs because they were only 6 months old.