Welcome to HU & bravo for starting 2011 with such ambition! You're right to be concerned about the weather. It can be pretty rotten the whole way down your route and WILL be very cold.
Of course, there are plenty on the Hubb that will tell you to wrap up warm and go for it (some residents here have had their senses numbed through years of motorcycle related abuse), but I personally wouldn't do it. You didn't mention whether you were thinking of doing it 2-up or not. From my experience, she will hate every minute of it - for the most part they enjoy the thrill of zipping along and looking around at the scenery so riding 12 hours a day for 3 days in near freezing conditions (before you add the windchill) with the possibility of minimal visibility whilst freezing her ass off may not appeal!
I have ridden to the south of France before in winter (no fun) and my brother in law lives in northern Italy which appears to be colder than the UK's winter for the most part so he doesn't ride in it (and has snow chains on his car a surprising amount of the time).
I know it must be a tempting idea, especially as you've just got your first big bike, but personally i'd save it for later in the year. 6 days (you're gonna have to come back eventually!) of semi-decent weather in Feb is a big ask. And we haven't even talked about snow and ice...
Hell, maybe you'll love extreme winter riding but it's seems like unneccesary pain and suffering to me (and I'm an all weather rider when I'm in the UK).
Just my opinion, and you may get replies saying go for it. Good luck if you decide to go for it, but if not, have a fantastic spring and summer on your new salt-corrosion free bike!