How do I pin an objet in world-space to a UV co-ordinate on my globe?

Here's my spinning globe: http://i.giphy.com/3oEjHHALmZQHHQrRyE.gif

It's a sphere, and I'm effecting the UV offset of a world map JPEG. I found that spinning my globe any other way, using RotateAround for example, became very awkward to use.

If I wanted to pin a flag to, for example, the texture co-ordinates of Great Britain... How would I do that?

I did get very close, using some trigonometry on the texture offset vectors... but I just don't know how to use those functions on 3 axes, I got stuck on the Z.

Alternatively- if there's a better way to drag the sphere around in a predictable, friendly way, then do shout it out. Then I could simply make my flag a child object.