Absolutely one room at a time. We started with the biggest things first because it does get to a point where you run out of steam and that's when you can temporarily stop or move onto something that's an easy hit to reinvigorate you! My hubby always says do the lounge last, otherwise you have a nice room to sit in and it gets too easy to leave the other rooms It's worth waiting for, and paying a bit extra for, a good tradesman (and never pay for all the work upfront), but they can be booked up a long time in advance so bear that in mind when planning when you want works done. Know that you will be living in relative chaos for a while and that project managing everything is almost another full time job. But also know that it's really exciting to shape your house to how you want it and that the end result will be well worth it