I've researched the symptoms for fault code P1109 on this forum - mine is temperature related i.e When the car is really hot after a long run it kicks into Limp Mode and I cannot clear the fault until it cools down sufficiently.

I know the code is now down to the Swirl Valve Actuator throwing a fit and causing the code and Limp Mode, but it doesnt always happen and clears when it cools down.

It appears that the crud that has built up in the manifold causes the Swirls to stick at high temperatures, thus jamming them and making the acutator think its failed therefore throwing the error code up and leaving me Limp.

I've taken the car back to the trader and told him I expect nothing less than a new manifold now - and the diagnosis is all thanks to the knowledge of you guys on here and some persistence by me in trying to replicate the error.

Thanks everyone - as always everyone has been a great help!!