How much savings are there to be made? Is it wooden blinds, which can be very expensive or straightforward plain old roller blinds with a white/cream finish. I got house of blinds fitted last year for around €500 (there were about 9 blinds) from a local guy and was very happy with the blinds and finish. Some of my neighbours had mixed results when buying blinds both online and from blind shops. I just find it hard to judge quality when all you have to go on is a swatch of fabric.
The finish/stitching etc varies differently from each supplier. Also, some of the suppliers give you plastic beads at the side, for the side chain whilst others give you stainless steel, which looks far smarter.
There are a number of people here saying B4i are great and perhaps they are, I just would be weary of measuring/hanging etc, particularly drilling into tiles in the bathroom. I did see the guy hanging them and it did look easy, so I suppose a handyman would do it fairly handy.
I suppose it would be safer to buy like Pantone, Velux, which is a brand, so the quality can't vary.
To the OP, I would shop around, online can be /but is not always better. Get a couple of quotes from online and local before you go with it.
Good luck with it.