you could put some newspapers and straw to keep it dry so I do agree, just make sure you wrap the box with waterproof bag or something to stop it from getting damp or wet.

Thank you Wildlife.... glad I saved some boxes! I will also put the other stuff in and will empty compost bags do as liners for the outside?

But if you wrap in waterproof make sure its all quite dry first of you'll get mould under tha wrapping..I wouldn't risk it.
You could put them in your boxes and then just cover them with dry compost, sand or peat and leave it at that. Its all you need to do apart from keeping them in a frost proof shed or garage etc.Just keep the mice away.

Last year I over-wintered my Dahlias by lining blue plastic mushroom trays (the ones that stack upon each other) with newspaper, filled with dry multi-purpose compost and laid newspaper over the top. They stayed in the unheated greenhouse and all bar one came through.

Thanks Shirley and Steragram.....will keep an ey open for the mice!!!

There's a lot more to overwintering Dahlias successfully than meets the eye.

For one thing they should not be allowed to be stored completely dry over the whole winter or the tubers could well shrivel up and die.

Good video showing a foolproof method (3rd one)

http://tinyurl.com/o6nnvut

https://www.youtube.com/watch?v=hfRhty53LNU

is the video to watch. The two people who have made the video are top growers, showing their methods.
Both say, along with the rest of us, that the compost to store them in has to be dry.

What it shows is that the best way is the one that works for you.
The way I do it is here.

http://growingforshowing.blogspot.co.uk/

Thank you Scrumpykat and Bendipa for the advice.