What kind of curtain rail and opener?

The window hole is 2.5 meters wide:
if i had curtains which fully covered it I would be warmer.

They are behind my desk so opening by a string or similar would be good.

How to seal them at the top and sides?

Wall surrounds are OSB.

Or blinds?

Insulation is the main aim.

Could they be used as a projector screen for movies?

But £149 is too much for a screen which might be used once or twice
https://www.viking-direct.co.uk/en/n...3-cm-p-4332258

Ideas and experiences please?

[George]