how will my baby fish survive winter in my garden pond?

I really need some advice. I have a small pond, in my garden which until this
summer housed 4 goldfish. I now have the same adult goldfish plus an excess of
10+ small fish! They range in size from 2cm to 5cm. Is there anything I can
do to help them survive through the winter, as the pond tends to freeze. The
pond is about a 1ft 1/2 deep and 5ft long. I have no filter or heat element,
but have substantial vegetation. Basically the pond up to now, has been left
too its own devices. Any suggestions would be appreciated