Perhaps you could replace them with black out roller or roman blinds?

Window shutters maybe?

i have a radiator under the window in my living room....i put long curtains there as by the time they are drawn, the radiator is either off or cooled right down.

You could leave the Venetian blinds for light & privacy during the day and add Roman blinds, mounted above the window so they cover the sides too. Like this...

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Agree with petersmummy. I'm rather sleeping in a cool dark room, then a light warm one.

Which ever style of blind or curtains on the outside of the recess will allow light bleed at the edges. It’s difficult to see how deep the recess is, would there be sufficient space for a 25mm Duette black out blind to sit in front of the existing blind? The fabric goes right to the edge of the cassette making the tightest fit possible for any blind style. Luxaflex have an operating system called Literise which would work well. If there is insufficient space for a secondary blind, you could replace the existing with a ‘day and night‘ Duette, it would be a pity to waste your existing blind though.

Following!

I'm with Carolina, put up Roman blinds on the outside and they will cover the whole window at night. That's what we do in a lot of our rooms.

Thanks for all the comments. I was toying with roman blinds over but hadn’t seen a clean execution. @caroline thanks for the pictures really helpful !

I would recommend recess fitted black out Romans (measured exactly no gaps to let light in) I measure it so that it has the smallest give ti allow a smooth raisun and lowering. I also black out curtains. Even the a sliver of light in my bedroom keeps me up.

I agree Patrina. I have black out blinds, black out curtains with additional black out liners and a pelmet to stop light spillage. Chink of light and I’m awake!