Boy that's a lot of information to take in, it took me ages to read it all, its nice to get a full and helpful opening post though, not like some people who just post a seemingly generic question and expect you to know what the hell it is they're going on about.
Anyway, do you mean the pitched roof or the flat roof on top of the dormer?
Haha, sorry yes for the brevity, im meaning more along the lines of ..
What is the minimum height of ridge, angle, size sqm of loft conversion to make installing on worth worthwhile. I read that the ridge must be 2.2m above finished ground floor ceiling level to be building reg compliant. Ill take some measurements today and post a pic. Its a single storey 80s, detached, bungalow, interested in whether a dormer type loft conversion will work in this instance. Whats the approximate costs etc, a website said approx 21,000, which i imagine would be recovered if the bungalow was sold on at a later date.