I can't actually answer your question as we've only recently had our 2 buns (2.5 weeks ago) and so this coming winter will be our first. Ours have their hutch in the shed so are like doubled up with housing and if it gets really cold I'll still put a blanket over the hutch as the shed can be draughty. I'll also increase the straw in their bed chamber (I read somewhere that in deep winter they should have a whole bale of fluffed up straw to snuggle into at night). Other than that, I don't know. You and I are learning together by the looks of it.
I would think that make sure where the kennel/hutch is, is not in direct line to get full windy blasts (i.e. not in an alleyway or at the bottom of one) and you will need to cover the hutch with at least one blanket at night (has to be waterproof too I should imagine) or somehow block off the mesh part of the hutch to help keep it dry/wind free. Watch their water doesn't freeze by changing it as often as necessary when it's really, really cold. Also, as mentioned above, lots and lots of straw in the bed chamber area, with a decent thickness of newspaper and/or shavings on the bottom of it to raise them up off the wood a bit more. I think you can get special heat pads too, or even hot water bottles - but both will eventually go cold in the night so don't know if they work or not.
I would think that someone with plenty more experience than me will give you further advice but that's all I can come up with
edited: told you! Sky-O beat me!