Where are you wanting this in relation to your and neighbours houses. Do you have drains anywhere near the planting site. A pergola with clematis montana growing on it might give you the height without falling foul of privacy/shade legislation. 6' is considered to be adequate to give you privacy from windows on the ground floor.

Clematis are great in the summer. You can buy a few so that once one finishes flowering the next one takes over. Trouble is you don't get much cover in the winter. Have a look in other peoples gardens near you to see what grows well. Local parks with walled gardens are a good source.

The direction your garden faces will also affect what will grow. My garden sounds similar and I have one side of garden in shade and one in sun needless to say it's easier to get things to grow on sunny side. Passion flowers grow quickly and mine need very little attention. Also for temporary screening I plant giant sunflowers and sweetpeas.

I've added this question to GoYpedia screening ideas and climbing plants...
click on the headings over to the top right... might help with ideas :o)