Flip / mirror uv's imported from ZBrush?

Hi Folks,
I’m trying to flip the uv’s on a uv’ed import from ZBrush.

Whilst I can flip the uv’s i.e rotate them 180 degrees I am doing so it seems in their local position i.e they are rotated but still at the bottom of the uv grid.
I need the uv’s to be rotated 180 degrees but so too their position to be mirrored in relation to the uv square i.e rotated 180 and at the top of the uv grid as if you have spun a square of paper.

Help greatly appreciated on this matter.

Blender 2.74 using cycles.

Ok I have it figured out - the image texture is 2048 x2048 , in the uv/image editor window press n and change the cursor location to x1024 and y1024, select the 2d Cursor option as the pivot for Rotation and Scaling >uv’s >mirror y and hey presto.

Glad you found it.
The basic idea is always scale (x or y) =-1 for mirror
However, next time flip coordinates vertically when baking in zbrush. (options are there)