In reply to Mountain Lass:
> Is the weather likely to be significantly affected by the later date please?
Yes. It will of course be colder, and there's very likely to be fresh snow, so great care needs to be taken if you're crossing a 'wet' glacier as the crevasses are very likely to be covered over. Many of the huts will be closed, though their winter rooms will remain open. Also, many of the lifts/cable cars will also have closed (you can easily check online for the opening times of the lift you'd use for the Breithorn). I hope that's of some help.
