You could try resetting the ecu; worked for me and costs nothing. Just disconnect the battery for 20 minutes or pull the fuse for the ECU which is in the fuses/relays box under the bonnet. Press the brake pedal while battery is disconnected to drain any charge left in capacitors. The ECU will then relearn the sensors and this may fix the problem. If it doesn't you havn't lost anything !
Have not had long and developed this problem - Idle steady at 1200rpm at cold start but when warm hunting between 1000 and 1800 revs.
Looked on here and saw others had had same problem and removed ECU fuse for an hour whilst also cleaning the battery posts and terminals wich were minging.
Replaced Battery connections then ECU fuse and the car alarm promply went off !
Have tried shutting all doors/tailgate/bonnet locking unlocking to no avail, alarm keeps sounding off.
Pulled fuse for alarm and still keeps going, and engine starter dead.
there is an immobiliser flashing to right of steering wheel on dash, have touched the immobiler fob to it but makes no difference.