Evergreen or deciduous?

Anything fast growing will have an extensive root system to support it.

True! Probably best to put up a strong, permanent trellis, and grow fast vines on it.

What about planting budleija, and leave them to there own devices, quick growing, just take a few of the side branches out as it grows and leave the height alone, good for screening awkward areas, and lovely flowers for the bees and butterflys, or whynot put some sturdy trellising up to the desired height and grow some clmbers up it eg russian vine[ mile a minuit] or a rampant clematis montana.

I have to recommend that you pay a visit to Annella's pages. She has a wonderful mixed 'hedge' of screening plants all around her garden. Some are just slender until they reach the top of the fence, and some are bushier. Some evergreen and some deciduous. She is the master of quick screening! :) I think if you have a look at her pics you will get some great ideas.

I have used Eucalyptus, Cotoneaster Exburiensis, and Photinia Fraseri (bought as a standard) for this task, and Pittosporum also grows nice and quickly and can be pruned into a tree shape. Magnolia trees grow quickly too, but be careful, some are huge trees. One I have, 'Heaven Scent' is a good choice. In my first garden I grew a wonderful Hoheria Sextylosa which is evergreen and has lovely white flowers in summer, but it is not good in exposed sites.

Hope you find what you are looking for! Karen

That happened to me I planted a few Mountain ash, they dont grow big, but big enough not to see the houses at the back. The berries are lovely for the birds in the autumn.