Poor you, I presume you mean upstairs windows? So dont think there is any shrub that will tick all your boxes! Just to remind you that like fences hedges can now be limited to 2 meters, we may be enforced if a neighbour complains? But if you have the room? a tree/s such as Mountain ash, Plum nigra, Laburnum, I have these down one side of my garden about 6 ft from the boundary and it would help reduce the affect in your situation.
You may need to work out the perspective before planting? As often trees plant some way up a garden give a better block out affect than those planted directly on the back boundary. Lastly if your neighbours dont want the shade they should stop their children shouting at neighbours!

what you can do which isquit legal andquit cheap is to battoni8ng from a builders merchants and make your own 10` pannels of trellis or maybe a low fence and make the rest up with trellis pannels and grow some nice climbers up them . it should do the trick nicely .

Buddleia certainly grows fast but wouldn't do the job in winter. The trellis is a good idea & would be instant, but you might have problems with the height if you plant on the boundary as Drc says. You haven't said where you live or which way the boundary faces, which could affect what sort of climbers you might grow.

its legal steragram as trellis is deemed a plant support . you can have a6` fence with a 6` trellis on top if you want .

Cunning!
S

and handu if you want quick legal privacy x .

I see Magparker has thanked you for the suggestion as a separate question NP.

ow i didnt realise steragram thanx for that xx .