My previous post included a typo and annoyingly I can't edit it.
We stole 25cm from our bedroom ceiling height and gained around 40cm head height in the loft space. Sorry for any confusion. (Delighted with the result. We had already arranged too be out as we were doing side return at same time)

We are having ours done at the very moment in time!

I was very impressed when we came back from a day out on Saturday when the builders had put down this clear sticky film onto the carpets in the hall way and stairs to protect them.
And they had put some kind of plastic sheeting on the ceiling to catch the dust from falling in the first place.

I had also purchased these Dust Stop Zip Dust Doors for when they put the stair in etc. They look like they will work a treat.

http://www.ebay.co.uk/itm/Dust-Stop-Zip ... 19e9c69223

removing ceiling is a win win, so long as you can afford to move out. this means the new loft floor can be a lot thinner, with the main steels and typically 200mm deep timber being the main 'depth' elements. when you keep the ceiling over first floor then the new loft floor has to sit independently over this - losing head height. an extra 100mm in the loft headroom can make the difference between a great space and a hair singeing squeeze!

You should also consider lowering your bedroom ceiling a little to gain height in the loft. Our bedroom ceiling was very high so we stole about 25cm to gain 20cm in the loft. We didn't notice the change in our bedroom but it gave us vital head height in the loft so we were able to tuck the shower in a nifty place and it also have us more usable floor space in the loft bedroom. It's worth studying head heights carefully as some people spend lots of money on their loft and end up only being able to stand fully upright in a small part of it.
Having said all that, this option would obviously add to the disruption and mess that you're trying to avoid.

without doubt, when the hallway is broken through - dust will come in, so be prepared. i have yet to hear of a loft conversion where this didn't happen.
are you aware of all the design decisions to make when undertaking a loft? has a professional (or other) advised you on the process and details to help you best understand possible internal heights, best construction details to ensure your loft is warm in winter and cool in summer etc etc?
Lofts cost somewhere in the region of £50k - a lot of money - make sure you know that you are getting the best solution - an architect is for sure the best way forward to get a 'specification + drawings' on which to ask prices from a number of loft companies/builders. this set of information also helps mitigate escalating costs through the build.
an architect!

Your mention of 'totally done the house up' rings slight alarm bells. Be prepared (at the very least) for:

Redecoration to hallway all the way up (they will probably tear into the hallway walls to run cables and pipes up, not to mention leave grubby marks everywhere), carpets may need replacing in hallways (they will probably protect them but still they may never be the same again), exterior redecoration (we had smears/splatters of cement in numerous places on exterior of house and garden wall and holes punched through wall and left open at eves level. Be prepared for some damage to your garden.

In addition there's the unexpected (foot through ceiling below), urine spread across ceiling. The builders were peeing into bottles in our loft (despite the fact that we paid extra for a portaloo outside) and they spilt one bottle urine onto the ceiling of our forthcoming baby's newly decorated nursery.

In addition, if anything goes wrong with the building work be prepared for a long haul. Our loft company had not followed building regulations and it was picked up by the building inspector. As a result the loft company downed tools when asked to put it right and it took over a year and a temporary expulsion from the Federation of Master Builders to get the loft finished. You could reduce this type of risk by having an architect draw up a proper contract and help you chose a good builder though. Personally, I wouldn't use a loft company if we ever did a loft again.

However, I think a loft is probably less disruptive than a basement or a side return!

I agree that it's better than a side return, but not by much. At one point every room in our house (which was renovated only two years before) had some sort of damage to it. I wasn't expecting it to be that bad. It also went on for much longer than we thought it would, but some of that was to do with the builder not doing what was promised. Basically you can live through it, but it's unpleasant.

Compared to other renovations I didn't find our loft too bad, as it is all happening above and until the knock through to put in the stairs it really isn't that bad. You do get some dust but we sealed the doors of rooms we don't use everyday and the ones we do split plastic sheets over them and keeping the doors closed kept the dust at bay. Also getting a good clean (post building work clean) at the end is worth it. We did our loft pre-kids so can't say how it is with children though.

its OK

you'll always have dust and hassle but you don't need to move out.

wouldn't want to revise for my GCSE's with it going on but its ok

Let me use a birthing analogy

A loft is like Braxton Hicks, there is stuff going on but with a stiff drink and a bit of focus you can get through it as it's over so quickly.

A basement is like the contractions at the start. It's getting serious but its not REALLY bad.

A side return is like giving birth. You really just want to be somewhere else