To cut out the person from the background and have a decent result will be nearly impossible here.
However, if you intend to use the 'cutout' on another background there's a nice and usefull technique to achieve something like
Eggy - that looks really good. Would I be right in thinking that if you follow this procedure but with an even higher contrasting background and then merging all layers to a single layer (ctrl+Shift+alt+e on the top layer) you would have a better chance of using the refine edge tool to get a better result than the OP?
In this particular case I don't think a better result is possible due to the fact that the loose hairs are way too fuzzy and PS wont be able to calculate the 'borders'.
But usually people cut out persons in order to put them on another background of their choice. In the used technique you will not lose one hair.
I you look closely at the loose hairs on the left side (shoulder) you'll see that the illumination of those hairs adapts to the background. The 'sky' background is bright and therefore there's a subtle see through illumination.
In the original picture you have a dark background and almost no illumination of those hairs.