We moved in about 4 years ago and still can't afford to redecorate. We lived with odd curtains at either end of our room for a while but then opted to put up some secondhand roman blinds at one end til we get sorted. I couldn't be too picky about size so mine hang outside the recess.
You man is right, there
is a gap but it's not too bad and not terribly obvious although it depends what you mount the blind on. Ours is fixed to a wooden baton. We have another RB in our downstairs loo - also hung outside the recess but mounted on a proper RB fixing - this hangs further off the wall. Again no real problem as long as your blind is wide enough.
A few things to consider whichever fitting you choose. Are you covering a window that you use quite often for ventilation? It's easier to leave a small gap in the curtains to allow airflow. RB's look a bit odd if one isn't fully dropped and the weights in the bottom may mean they bang/flap when the window is open. Hanging blinds outside the window means that you can use the windowsills. This is more difficult with a recessed blind as you're more likely to knock stuff off.
Take care with your choice of winding/dropping mechanism. We have metal chain winders in our main room - they are very noisy and mark the fabric. The one in the loo is a locking string type. Cleaner and neater in appearance but a tricky beast to operate. The angle has to be just right to release the blind. My teenage kids can't make this one work at all!! I also have to lift the blind out of the way to reach the string behind. Grubby fingers would mark the fabric and even with care it's possible to see where the blind is handled.
I have to say that the windows look undressed even when the RB is hung outside the recess. If I decide to keep mine I'm planning on hanging a false curtain to improve the appearance. The advantage of a false one is that you need only a small amount of fabric as the curtains will never need to close. The pole can also be used to hide the top of the blind. Alternatively you can dress the windows with a boxed valance which also looks very effective and again, hides the top of the blind.
Here's a couple of online companies with good advice but there are loads out there if you need to compare.
Pret a vivre and
Kurtinz.com Good luck with your choice