So...
I have bought new spark plugs to see if it will cure the problem as they needed changed anyway just waiting for them to arrive, i have already taken the old ones out and they are fairly knackered looking.. at 135k there is no history of them being changed..
But i did clean the old spark plugs, made sure all connectors are in tight and reset the fault codes and its running 90% better (no more breaking up while driving, just a small misfire while idling) so hopefully the new plugs in will help