Thanks MKG, and yep you're right about the anchoring issue! In the lower wall (about 7ft) there are already eyelets for wire, but the big wall hasn't got any that I've seen so that will be a bit of a problem. There are two hooks on the lower roof (11ft) which I can use too for that really thick chicken wire trellis-y stuff.
I'm toying with the idea of something maybe like this for where there aren't walls/is soil for the anchor pole to go into:
As the big wall is about 16ft tall but only 2 feet wide (the rest is our windows) might be better to do something more along the lines of making a 2 tier wooden planter with trellis attached to the back and just growing beans/peas/achocha or maybe train squashes up the trellis. I've got centiflor type toms for experimenting with in hanging baskets, and 4 other vine varieties for elsewhere.
Anyone any idea on sizes for containers for squash? I've not grown them in pots before, also as I'd be using multipurpose compost in the pots (no mud) would I need to manure it first still or would that be nutrient overdose?