Originally Posted by Three Dawg
No, deffo a 2.5mm. Socket does work as stated because the headphones from my mobile (cell) phone play the spoken instructions, one side only though. All the cables etc are brand new. It's like the spacing on the jack connectors (the gaps between the insulator bands on the jack) is different which is perhaps why the stereo plug off my phone works, albeit in mono.
Your phone headset should have an extra band on it for a microphone. Perhaps that's why it's in mono. Can you just take it to a store and try out some other headphones on it? I've never been to Bonnie Scotland so I have no idea what to expect there. I know we have some small enough shops here that I could park the bike right out front and walk out to try headphones at several.