Not very! So I spent an hour or two giving the cab a bit of a scrub. I took the control panel off and gave it all a wash in soapy water.
I then gave the outside of the cab a clean first with some warm soapy water and then with a white Magic Sponge. This is a great little thing for clearing off scuffs and scrapes.
After that I gave it all a quick polish with some white T-Cut before giving the whole lot the once over with window cleaner spray. Not sure what use it was on the metal parts of the cab but it brought the monitor and instruction strip glass up nicely.
I still have to give the inside of the machine a clean down along with the electronics. Obviously this is a big enough job which requires a strip down of the cab to be effective. This will probably go on the long finger.
No photos of the cleaning as its difficult to show the improvement to any great degree.