Well, the install is finished. It took about 2 hours to do the entire conversion including placement of the coax for the GPS aerial (but not the aerial itself, count about 15 mins extra for that)
The wiring harness needs only a very small modification. There's a plug (with only 2 wires) which needs to be replaced and that's all (the Comand uses a different plug for the CAN-bus).
When all is finished, you need to go to the dealer to activate the pictogrammes under the speedo (they do that with their diagnostics thing).
Everything works fine with the steering wheel knobs, just like if it was fitted at the factory. There's no difference at all.
See pic.