The first bit of hedging we planted was needed in a hurry so we bought a bundle of 50 Rosa Rugosa from Buckinghams, mixed red and white. It means you get a pretty hedge, with flowers then huge red hips, plus it rapidly becomes impenetrable. It won't be as tall as you want in the first year but it can rapidly reach about 7'. You trim it with a hedge trimmer, at an angle so you get all the flowers on your side, from the fresh growth. They are very cheap and councils use them a lot to keep out unwanted youths (unwanted in the council's eyes), to look good quickly, and to be easily maintainable. I'll see if I can find a link, as I'm not totally sure of the name.
I've just checked on Google - 'Rosa Rugosa images' and that is the plant I mean.