Buy quality...do the job once, they said...
 

So I bought a quality PIR detector for the wetroom I've constructed for my wife.
It's mounted in the ceiling and switches on four LED downlighters plus the vent fan when you enter the room.

Trouble is, it also switches on when you open a door to that area. The other night it switched on when someone opened the front door, which is a good fifteen metres away, right through the house.

And when we had high winds the other night, it came on about every two minutes.

Going to try pulling it out of the ceiling and wrapping it in a plastic bag. If that fails, it's coming out and going back for a refund. I'll go with a ceiling pull switch instead, but will have to fill and plaster the hole it's presently in.

Its not a sound and PIR detector? Ive got some for my garage, so long as there is sound the lights stay on if the pir doesnt detect my body heat

No, it's a Levante DLCPIR Three wire, mounted in the ceiling.

Are they not adjustable for sensitivity

Aye, and it's turned to minimum.

Try sticking insulating tape over the lenses to block out some the the IR fingers until you get it where you want it.

We used to do this with PIRs for intruder alarms to let pets walk around certain areas.

We have a loft extension and fitted a PIR in order to turn the lights on when coming up the stairs (or going down). First one we used was so so sensitive, a sparrow fart in the garden would set it off. Replaced with a better unit and set it on a timer (so doesn't come on at 3AM for instance for no reason). The issue is that they are highly air pressure sensitive, so when its very windy, air comes up under our eaves and triggers the sensor. I imagine similar for your door. As a suggestion I would try and isolate it from the ceiling void - maybe an enclosure up there just for it? Wrap it in some old cloth?

alarm PIR are better with dual trigger (infrared/microwave) to stop false alarms,