Hi Leon, I've bought my kids boots made by Outdoor Scene, which can be got for around £50. They are not the best boots in the world, but there is no point in getting expensive boots when their feet are still growing. These boots have lasted my son for a year and now my daughter is wearing them. They have been waterproof, fine for easy hillwalking, 10 mile hikes and for scout camps. I guess that they have lasted for two years use so far, and they are still good for some more.
Hope this helps,
cheers,
Doug.