Yup, tile to ceiling then fit extractor. If it’s a new build the extractor is compulsory anyway! So if its not its obviously just good building practice (damp being #1 cause of black mold). Your extractor should have a certain flow rate (call your building control officer at the council, he will advise) and go one higher, I learnt from experience you need a bit more than they spec, you should lag the flexi hose above the ceiling or you get condensation on the outside of the hose in your loft which will drip down on top of your plasterboard ceiling, You should mount it above the shower or as close as. You can get humidifans for a few £ more than standard timer fans and will get you brownie points with the missus. You should paint the ceiling above the shower (in fact your whole room) with something like Dulux matt bathroom wipe-off emulsion, not just the standard emulsion stuff. You should defo tile to the ceiling as steam WILL condensate on the walls, so paint will just look and perform rubbish after 6 months anyway. If the rest of your bathroom is only half tiled you can get over the look of a block of unwanted colour in the shower area by following your tile colour scheme from the rest of the room and for the 'to-ceiling' bit just use plain tile (eg white tile on white paint wall?) to compliment your wall paint. Grab a load of freebee bathroom catalogues in the diy shops and look for their tricks like that. good luck - nice project once done. Stan