Sorry Bev, Peccavi knows next to nothing about cars - just what wikipedia tells him. In the old old days cars had a choke in the carb to restrict the airflow when the engine was cold and as it warmed up the driver had to gradually push the choke in for even running. Then we had automatic chokes that did it for us. Now that we have unleaded fuel this is probably managed by the engine computer (Engine Management System - Engine Control Unit etc) to reduce the poison gasses you get from cold running engines - but I'm not sure.
I would get the vehicle properly serviced - a decent garage should be able to sort it out for £££ - they probably see faults like yours from time to time.
My guess - and it is only a guess - is that it's not the TDC sensor - the sensor tells the computer the precise position of the rotating parts in the engine - same difference cold or warm - the sensor either works or it doesn't work. Your sensor works OK when the engine is cold so why should it not work as the engine warms up?
It may be some other sensor or it may be the computer unit.
Good luck...
Peccavi
March 2010
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.