I've had every other type of blind bar Roman. I even made my own gathered blinds a few years ago only for the flipping cord to snap. I was not happy. Now I have simple roller blinds and Venetian blinds.
I have seen Roman blinds in IKEA so that might be a place to look @gibby.
A friend of mine made Roman blinds for some of her rooms and regretted it. They need constant fiddling to get the pleated effect of the fabric to look right and, from memory, there were more than the usual number of cords involved so all a bit messy really. She replaced them soon afterwards.
The cheapest way to buy blinds is online - we've used 24/7 Blinds and they are excellent, always have offers, lots of choice, great service but they don't have a fitting service. It still might work out cheaper to buy blinds from them and get a local handyman to fit them rather than going to someone like Hillarys who offer the whole package (they are massively overpriced) or a local independent blind shop.
I've made quite a few Roman blinds and I really like them. If they're well made, you shouldn't get any trouble with them, they should lower and raise easily.
I've recently got a new micro Venetian from www.blindstogo.co.uk and I'm really impressed with the service, they do all sorts of blinds, including Romans and you can get free samples before ordering.
I made one years ago for a small downstairs loo window. I vowed never again. Like Nellie's friend it was fine unless you fiddled with it but I think that was more about the fabric than the blind itself.
Some I have fitted inside the recess, others outside. I would say it's easier to fit outside because then you don't need to worry about your measurements being too precise, as long as you've allowed a couple of inches either side of the recess, it's fine. Blindstogo also have a helpline, which I found useful, as well as measuring and fitting guides.