Thanks for all of the posts so far on this,

Looks like I will remove the insulation from under the bonnet and see how i go. I didnt stop the car and restart while in traffic for fear of not getting it going again, i knocked it in and out of drive as i stopped and started for fear of it stalling while stationary. Incidentally the exterior temp displayed was much higher the real temp outside and i suspect this was due to the tropical conditions under the bonnet.

I would describe the car when hot and on tick over as 'hunting', with the engine going from barely running to around 500 rpm and back again.