well, no magic wands!
my first thoughts are pretty predictable- pyracntha or ivy.
there are plenty of ivies that are not just green, but green and gold or variagated, also those with larger leaves. you might want to start off with more than 1 plant as you've 12ft along to cover, and it's pretty low maintanance. clip only if required in spring, and of course good for wildlife and will berry when mature.
pyracantha is an evergreen shrub that you can pretty much clip to the size you want, my parents have a large one up to the bedroom windows and across their house, but it doesn't come out further than 1 ft. it has pretty insignificant white flowers in summer but the bonus is the berries in winter, orange or red depending on the variety. some have less vicious thorns than others!
coteneaster also-plenty of those to choose from, some keep their leaves better than others. (try 'google').
you can also get (although unfortunately i don't know much about them) climbing hydrangeas which are supposed to be self clinging, with white lacy flowers spring/summer.
if you're growing something like the pyrancantha or ivy, you could try clematis growing through them to give additional colour at various points. if you go to the rhs website and access their plant selector, you can see all the clematis that are suitable.
maybe someone else will have some more ideas...................... :)
