Thanks for the comments, suggestions.
The bike is a 2005 model K1200GT and if you want to register the bike onto French plates, which you should do after one month of living their you have to go through all sorts of hoops and provide documents of conformity from BMW, etc, etc, etc.
I agree why bother, I have a hayabusa which is 175bhp and no way am I going to restrict that BUT if you ever had an accident the first thing they will ask for are papers, etc, especially if it is 'an import' so to be safe and ensure insurance is valid, etc best to do it right.
If it can't be done cheaply then, as I mentioned, both bikes will have to stay at my moms in her garage, although she doesn't know this yet!! I would have one bike over for 6 months then bring the other one over and that, in theory, should be OK even thought they should have plate change after a month I think I may be able to get away with that.
What a nightmare!!