Help with Goldfish

Hi I live in Scotland,so as you will probably guess we don't get great
weather,I have had my pond for 3 years now and so the fish are about that
age lost a couple of fish in the last month,not sure if this was the
freezing weather.
Would like to ask why my fish have never bred,seems to me I must have been
very unlucky to have bought 8 male,or 8 female fish.
Can anybody give me any advice on this,also am looking to buy some fish soon
different species but nothing to expensive,pond is big enough to add a few
more fish.
Thanks for any help given.