I have had this car from new and it has done 53800 miles. The timing belt was going to be changed recently but it was found to be in good condition and so just the auxiliary belts were changed. Immediatey after this work was carried out, the Idle speed for no apparent reason became erratic. As the engine was working ok before it seemed odd. But just to eliminate co-incidence the plugs have been changed anyway, and a new coil pack and plug leads change made no difference to the fault. The engine idles at about 900 rpm from cold quite happily, and seems to run normally. However when it gets up to normal  temperature, it cuts out when stopping but starts up ok. All plug/socket  wires are securely connected and no vacuum pipes have gone astray. The throttle body has since been cleaned along with the TMap Sensor. The rocker cover has of course been off to facilitate the timing belt inspection, but there doesnt seem to be anything out of place.  Is there anyone out there who can think what might have been disturbed. Prior to fitting the rocker cover, the timing which had not been disturbed, was double checked with the proper timng pin and  camshaft bar.

Turn on the ignition, do not start the engine

Turn off all accessories, lights, radio a/c etc

Disconnect the battery earth

Cover the earth terminal so nothing can make contact with it

Disconnect the positive terminal

touch the positive cable and the negative cable together and hold for about 3 minutes

DO NOT LET THEM TOUCH THE BATTERY TERMINALS

reconnect the positive

reconnect the negative

turn the ignition back off

take the key out

open and close the door

start engine BUT DO NOT TOUCH THE THROTTLE PEDAL

leave engine to idle for 10 minutes to get to full operating temperature

DO NOT TOUCH THE THROTTLE PEDAL AT ANY TIME

turn on the A/C on full power

DO NOT TOUCH THE THROTTLE PEDAL

leave to run for a further minute or so.

Off you go👍