Silliemillie - the candyfloss tree really does smell like burnt sugar/ candyfloss in the autumn. It can grow into a full size tree if you leave it (RHS Wisley has a great example) but I've had mine for 9 years as a screen and as the branches are very pliable (like willow) you can trim the top of the tree when it reaches the right height, then plait the side branches to make whatever shape you want - the side branches grow quite a few feet - so you could even train them along trellis at the top of your fence.
I got mine as literally a twig from ebay, and if I ever move, I'd get another one as the leaves are beautiful heart shaped. It's a real shame that it's not an evergreen though.
Like the others have said though, trellis & clematis are great - I've got mile a minute Elizabeth which I love going along the trellis, but my neighbours weren't so keen on it coming through their side, so we came to a compromise and I bought some cheap 'natural' coloured blinds from Wilko's, took out the fixings to leave just the strong fabric and staple gunned them neatly to my side, added a stretchy willow trellis on the front , and now the clematis can be trained on my side and the neighbours just see the back side of the trellis with the natural fabric screen. They like it and it gives privacy in the winter too once the plant has lost its leaves.