You'd be amazed how they can survive Rob. All mine, except for the Olive, got through last winter even though we had snow for 3 weeks. My collection consists of Acer, Hornbeam, Larch (go on all you Python fans - say in a loud voice 'The Larch'
), Maidenhair and Juniper. These are officially 'trees' but there are loads of shrubs that can survive our winter.
[Writes note to self - put together a 'How to make cheap small trees' essay and post it on the forum]
Honestly, you will be amazed how the little fellow's can survive.
Edit: That's a superb Acer you have there minimans, I'm jealous!