Had AA Man to look at battery - which i have never been happy with - tested again and all fine reading 12.4 - which i always thought was the minimum resting voltage? - but he also ran other tests and the battery is OK .
However he tested the battery with the engine on - and as he turned the ignition you could here the distinct crackle/snap of a spark - he immediately said my HT Leads are discharging to earth - and that's causing the misfire -so pleased i called them out albeit for a different reason
- will get new leads and packs ASAP . One simple diagnostic to remember for the future.