However they do work in my MP3 player. Not dropped my phone and they were working last time I used the headphones in my N900 - was wquite a while ago.

Can't see anything installed that may be making them not work.

The sound output is fine from the speakers - however when you plug the headphones in, the speakers just continue to play the output.

Any help would be appreciated.

I did Google this and tried typing in dmesg | grep headphone
in x-terminal - no joy.