Door curtains/coverings

Jackies

DH and I have sliding aluminium double glased doors in our dining room. There is no radiator in there and last winter we noticed (our first winter here) that it gets cold there.

At the moment there are vertical blinds (See photo) there which are good for summer as let light in and mean that people can't see in properly from outside. However I'm not massively keen on them (and they're old so have a bunch of blinds missing!)

To counteract the cold in winter I did think about replacing the blinds with a thermal curtain if we put up a curtain rail, but obviously wouldn't want to have them closed all the time. If we had the curtains open and no blinds it would mean people could see in which I wouldn't want

So basically i want warmth in winter and light in summer!
Does anyone have any suggestions as to how we could solve this?

N.B. Eventually we want to replace the doors with ones that open out rather than slide but this won't be till we decorate the room properly and have a radiator put in too, but this probably won't be for a few years