Just like to give a big thanks to Andy P. and also Samurai Performance in Braintree for finally getting to the bottom of my missfiring problem. Turned out to be two duff coil packs! One was breaking down when the engine got warm. This one was spotted by Samurai and was the worst culprit. Car ran much better but still missed at higher RPM. A morning with Andy and a lot of patience and we found a second dodgy coil! Very unusual.

Thanks again to both parties and anyone else on the forum who answered my queries.

Heh, it was nice to find something that was a cheap and easy fix. Shame it had to be number 5 that caused the problem though, becuase it's under the balance bar.