Flipping a UV map 180 degrees?

I have a UV map with two sides that I want to be the same, though I have mapped it so that I have both sides. Is there anyway for me to flip the other side so they match?

for flipping you can scale the uv’s to -1 in the axis you want. Select the faces you want to flip, press S, then the axis (x or y), and then type -1.
Doing it for both axis is the same as rotating 180º.