Hi all, I had a software update a few days before Xmas, before which everything was working fine.
A couple of days after the update i tried to listen to music on the original Samsung-supplied headset and the sound just kept coming out of the loudspeaker!
I've spoken to Samsung UK, who suggested a reset of the phone. Done that, and (quelle surprise!) no change - still playing out of the loudspeaker. It seems to me it's a fault in the recent update.
The USB-C still works fine for charging and hooking up to the PC, and I also tried a second headset - AKG headset connected via Samsung-supplied USB-C to 3.5mm adapter.
Blooming annoying.. get your finger out, Samsung!