New border, espalier plants

Hi there, 

so im designing my new border as this is the one I dislike the most. it get afternoon sun but in the corner is damp and dark. I'm thinking about piling 2 posts into the ground across the whole of my neighbours shed, prob about 7ft high and then running wireless across in a fan shape to make a espalier. I then want to put some ferns, actea purperea, digitalis and some others in front. 

I want an espalier across the posts, im think pyracantha, jasmine or a vine.. what do u think? Also, what other plants can u put in front of it?! I want to creare some height to hide my neighbors shed.. 

thanks