Agree with the consensus that the chopper is the way to go, there are (at least) two helicopter companies running NCE-Monaco, and they should include the hotel/office journey to/from the heliport in Monaco.
You may want to check with your airline, as I'm sure I've seen business class fares from LHR that include the transfer to Monaco. I'm sure bmi for one used to do this, probably others too.
Ken.
"No matter where you go, there you are!" - Buckaroo Banzai