Hi @Neil ... yes that's expected as per my last info. Picture taken with iPhone (=iOS) upside down but is compensated for by extra iOS specific info in a photo's hidden header data instructing auto-rotation This is fine for another iOS device like an iPad or another iPhone but not others devices (e.g. Windows or Android based). Hence why different viewers are experiencing different results.
To avoid this across-devices issue either the photos have to be taken the right way up to start with (which on an Apple device means with volume buttons pointing downwards) ... or a photo has to be stripped of device specific hidden data by copying it to, and saving it with, a very basic editor that excludes such data.
Sorry for the geekathon but this might be useful information in general for folk.