snip
Contact a local builder and see how much it would cost to render it. Not
as
much of a cost as you may think. Is it your wall to do this or a
neighbour's
wall?

It's my own wall... hence i'd like to DIY it ; )

Use cotton reels to stand it off. The latest ones are plastic so will not
rot

ok this i don't understand... am i suppose to put a nail or hook into the
wall & secure the trellis to it? where does the cotton reel come into play?

thanks.