Hey Mark. I'm sorry to see you here but you've come to the right place. You will get a lot of support here for many people going through similar situations as yourself.
The first thing I will say is think very carefully before you move out. Your wife wants the marriage to end, not you. There is no legal reason you would need to move out of the marital home. In the UK both spouses have occupancy rights so you shouldn't move out. Try to be strong in the face of it.
Secondly, what 'unreasonable behaviour' is your wife stating as a grounds for divorce? If there's nothing, make her wait. You don't have to sign anything.
I'm sure you're already doing it but try to keep signs of conflict away from your kids. Explain to your wife that you need to be seen to be getting along in their eyes.
Finally, I'll suggest you might want to read No More Mr Nice Guy by Dr Robert Glover. From what little you've written so far it seems to me that you, like me, are a 'Nice Guy'. Trust me, that's not a good thing when it comes to being in relationship built on mutual respect.
I have a WAW too and am already separated. I'm not giving up hope though as I think my wife is just lost. It's my task now to try and make her see that being married to me is a good thing.
Don't give up the fight Mark.
Me: 32, Wife: 22 Son: 2 Married: 2 years Separated: January 5th 2009
Sometimes you have to become lost before you can find yourself.