Ok, this is a really stupid question. For the PhD I'll most likely chose to do I'll need to move 6hrs away. I'm fairly picky with what I'd like to rent (been out of uni for a while) and will need to go lodging/flat sharing for a while before I can rent what I want. I've never been a lodger before, thus I have no idea how this works. Can anyone help?

Being 6h away from that town makes finding a room to rent somewhat complicated, though I'll be there for a week in early December. Would like to move just before Christmas. Is this sufficient with regards to timing?

What kind of termination periods do lodging/flat sharing contracts usually have? I'll move out as soon as I find the right place to rent. This could be in 3 weeks (unlikely) or in 2-3 months.

What's the best place to look for lodgings? I'd certainly not want to get a room in a student house but, being somewhat older myself with elder, quiet people.

Are you in the UK? Try spareroom.co.uk. Notice periods are usually 1 month; some may have a 3 month initial contract. Some might allow you just to give a week though.

Check whether your new department can email existing students - often people rent out spare rooms quickly for short term with no contracts etc