Should I buy Roman blinds that are too narrow?

[MamaBear7a]

I have a large bedroom window I would like to get roman blinds for. We are currently living with a duvet cover hung up on string so most things would be an improvement.
I fell in love with some fabric on a site a few months ago. It is now in their sale with blinds made to measure 50% off in the fabric. I've used the site before and I'm happy with their quality.
Unfortunately my window is 2.53m wide. The largest they sell is 2.4m wide. I am looking at black out blinds as I get blinded by the early morning sun otherwise. These ones would be 13cm too narrow, even with the frame taken into account I still think there would be a little bit of window showing on both sides. It is a three paned window so I don't feel i could go for two smaller blinds as it would look really odd.
So my options are - properly fitted £603 or too narrow £129.
What can I do to fill in the gaps?

For that difference in price I’d go with the poorly fitted to be honest! Then get some blackout material and Velcro strips and stick it up every night to fill in the gaps and block out the sun!

I'd go for two smaller ones to fill the whole gap. That wouldn't look any more odd then having a huge gap at each side.

Could you get the smaller blond and put it up in the centre and then get some curtains to cover up the edges? Obviously the curtains wouldn't close but they would dress the window.

Or would 3 blinds work? Have you got a photo op?

Roman blinds are incredibly easy to make so you should be able to get them for much cheaper than £600. Shop around, ask around.
If they’re too narrow they’ll look awful and bug the life out of you.

Could you buy the cheaper blind, and then get a curtain maker to sew a strip of toning or contrasting fabric down each side? My Dsis did that and it looks really good.