Sacha wrote:
We need a thick rapid-growing alpine evergreen climber which is not
thorny. Are we just fantasizing? Does such a plant exist?
snip

Judging by the answers and debate, I'd go for marine ply panels and
trompe l'oeil! Seriously. My former mil did that on a big slab of a
white retaining wall outside her kitchen window. It was an Italian
panorama and had arches, cypresses, birds, distant vistas etc. on a
wall about 30' long and 20' high - looked fantastic for years.

I'm laughing out loud, Sacha. Very loud!

And largely because because I've just dinner while looking down at said
corner with its pale green Calor gas tank surrounded by a handsome dark
green trellis, on one part of which is one great tuft of leafless
clematis, and because it's so clear that that gas tank has gotta "go"!

A great big trompe l'oeil, featuring what scene that would be compatible
with the very natural South Shropshire hills? I can't imagine what
would work . . . and work well! I'll take a pic of the corner tomorrow
and post it.

Eddy.