Here is the finished shade.
I bought mine from Primrose Gardens - they are called sail shades. Here's a link.
https://www.primrose.co.uk/sail-shades-c-85.html
Primrose now seem to have upgraded their offering for poles and you can now buy one's very similar to the one I constructed.
It's fixed at 2 points to the wall, one to a convenient tree and one to the pole.
I bought the fixings from B & Q.
You could just use a bit of rope to tie the shade up but I find the pulley easier for the pole. You could have a pully also on the wall ones to make it easy to put up and take down.
The pole is just an 8 foot garden fence post I've painted.
I also got some plastic drain pipe that it slides into.
I used a bag of 'postfix' to bury the plastic pipe.
I've got 2 fixings on the post.
A high one for normal use and one lower down so that if it is raining the water flows off it.