Thanks guys.
Thanks for that insight Duncan, I found the information very interesting. I'll definitely pay a bit more attention to head position, possibly get a video up.
After further prodding about, it seems that the pain isn't the shoulder blade tip at all. If I pull my left arm across my chest, so that the shoulder blade rolls out across the rib cage the pain doesn't move with the scapula. The pain seems to be localised in the muscle behind where the tip of the scapula usually sits, perhaps the Latissimus Dorsi? I'm certain that it's at some tendon though because there is a noticeable lump where the pain is (the lump is present in the same place on the other side so I'm sure it's meant to be there) so I think it's just that the tip of the scapula is aggravating this 'lump' in it's normal, retracted position.