I bought one of the fifty quid jobs from amazon, with the thought in mind that I'd probably be utilising the distance selling regs and sending it back as I reckoned it either wouldn't fit in the space above my stove, and I'm a bit skeptical too.
Very, very impressed! (Yes, it fits - just) the difference is quite incredible, from the point of view of how quickly the room heats. I can't say if it will be any warmer or not, as it's only been on an hour, time will tell with that one. I'm in an old house with pretty high ceilings, so it makes sense that the stove had to fill that space first before the heat comes down to sofa level, not any more though.
I don't think it'll be going back.
Edit - it's silent too!.