Advice: closing off the HT room

Hi guys, below is a pic of my HT room which has an open entrance. I could close it off and add a regular door but it wouldn't have that feeling of space. Ideally would like a solution where it could be left open mostly but then closed when in use. Sliding door? Concertina door?
Any ideas welcome, Im doing extensions at home and have the builders around to do the necessary...
Other pic is the view from inside the room
Cheers


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