Street Sound wrote:I think I managed to work it out in the end
.. but I still have trouble with the combined D/F# chord.. your thread about your elbow made me rethink how I was doing it - because hooking my thumb over the top of the neck was really hurting. So now I am up to the stage where I can do the song ok but hesitate on that one chord change... more practice of the fingering change I guess. 
How long does it take you to master a new song?
Yep - don't ignore pain...
The only thing to do really is sit and practice the change into the d/f and from that to the other chord, and then gradually try and do it a little quicker, it will come, just takes time
How long does it take to master a song - well it depends how complex it is... I've been working on 21 guns for a week and its not quite right, its getting closer, but I'm not good enough to play along with it yet... (well I was ok with the simplified version I was doing before my lesson, but I've been given the correct version now!)