| You say the garden bed is just under 2m wide - is this the air space you have to work with as well? Most trees with a height of 6-8 metres would have a width to match. If you are planting near a boundary, then nearly half of the width (and root area) will be on the other side of the boundary and the owners will have the right to demand that overhanging growth is removed. I am definitely not a lover of pine trees of any description, but the pencil pines sound like the logical choice. The other consideration is time. It's going to take quite a bit of it for any tree to reach 6-8 metres. You might like to consider roll down awnings on these windows to provide shade and privacy until the trees are tall enough to take over the role. I would also suggest that insurance is taken out to cover any future damage by invading tree roots to the neighbouring property. While there are many trees which are not regarding as having invasive root systems, old or damaged pipes which leak are an open invitation to any tree to "come in and have a drink". This step is more important when you are (a) planting near a boundary and (b) encouraging the tree to find its own moisture supply. | 
