None of beech, ash or willow are good against wind (dwarf
willows excepted, and they are too small). Look up Inverewe and see
what was done there.[/quote]
You can do better than dwarf willows. I have not imagined the willow hedges that are grown all over the inhabited parts of Iceland as windbreaks, although it appears that the possibility is not well known in this country. See in particular the comment on p12 of the following (I have cycled past the hedge in that picture and it is a very windy place, I doubt the poster lives in such a windy place since he is not in the Outer Hebrides - more normally they are rather more tidily pruned as on p5) but the rest is also interesting. http://www.windandlandscape.com/docu...Structures.pdf
The difficulty I am having is finding out exactly which species they use. After a bit of further searching, I'm beginning to wonder if it is S. caprea which PFAF notes is grown as windbreaks in places with maritime exposure, and is very hardy. The above document mentions S. phylicifolia (which may include S pulchra), but in a special context, so I don't think it is the normal one. Poplars, being a member of the willow family, are also grown as wind-breaks in exposed windy places. I've seen them quite high in the western hills in Norway, further north than Trondheim, and are also mentioned in the Icelandic context in that document. The thing about poplars is that they need an understory to provide low level wind protection, while they provide height.

Birches are also common in Iceland and northern parts of Norway. They tend to be stockier than birches seen in thi scountry. Maybe they are a suitable species, or maybe they just grow that way if grown in windy conditions. A lot of plants which do grow well in windy places don't actually grow so well in Britain because it isn't regularly windy enough (yes even in much of Scotland) - the lack of regular wind in Britian means they grow lanky and then blow over. Once you've been to Patagonia or Iceland you'll realise that Scotland, a few special localities aside, really isn't that windy. I already mentioned N betuloides, but N pumila is especially noted for this.