Who coordinates the trades?
Ask, because it is the difference between a renovation and a series of phone calls you make. Some quote as a managed job covering plumber, electrician, tiler and joiner; others price their own part and leave the rest to you.
Do I need consent?
Often not for a like-for-like replacement, but moving plumbing, altering a wall or adding a bathroom usually does. It should be settled at quoting stage, along with who applies.
How long without a kitchen?
Commonly two to four weeks for a kitchen and one to three for a bathroom, and joinery lead times often set the date rather than the labour. Ask for the weeks the room is unusable, not the weeks someone is on site.
Why is waterproofing worth asking about?
Because it is behind the tiles and you cannot inspect it later. In a bathroom it must meet the building code, so ask who does it and what certification you get.