Well, the islands are not treeless because of the climate or the soil but because of the sheep! Once trees have gone, sheep prevent them from regrowing. So if you can keep the sheep off, you should be able to grow yourselves a shelter belt. Trees recorded in the islands in the past include willow, downy birch and hazel - horses love those - and alder, which they don't. I don't see why you shouldn't give hawthorn a go.
