Two more things to try:
1) Try unplugging the ECM/PCU fuse, in the fuse compartment under the bonnet. This will cause the ECM/PCU to relearn the idle settings. Chock the back wheels and ensure park brake is applied, then idle for 2 mins in (D)rive, 2 mins in (N)eutral, 2 mins in (D)rive with...