Padsi1975 it's totally possible to live in during it, as long as whoever you use is tidy. They day they broke through with the staircase it was fine! Was shocked to come home and find it there! I wasn't home in the day which I think helped, and it was noisy when the steels go in and roofing, carpentry being done.
I honestly thoguht it was going to be more complicated than it really is. The builders broke in through the roof, then did most of the carpentry from teh inside (with the roof on). Then did steels and party wall build ups. We only had one or two nights where the back of the roof was open to the elements.
If you can give everywhere a dust and hoover a few times a week ou shoudln't feel too dusty. Although you do have a new baby, so during the breakthrough it might be an idea to stay with someone.
My only advice about usign anyone, would be to see who will be on site, and managing that site as you want to be able to ring them etc. I spoke to mine most mornings, just going through bits and peices.
We didn't know what the bathroom layout was going to be like and I couldn't picture it until I saw the actual space. The only stress was we had to order the suite quickly so plumber (who was on a deadline) could do first fix accurately. I did find myself ordering things asap, each week as they needed this or that, but if you know your tastes and what you want it's not too bad, for example all the light fittings are now same throughout flat and we know where to get them all.
I'm rambling now, and can only say it feels very very daunting, but once the back of it is broken you think wow ok I can do this!