Flip cubemap image from within the shader.

Hi all,

I am a bit stumped on this one and wondered if anyone could point me in the right direction. I have 360 degree stereoscopic images which I am using a cube map shader to display on spheres in my scene.

Everything was working fine in Unity 4 until I upgraded to 5 which caused my cubemap image to be flipped. I cannot change it via the Tiling or Offset settings so I am wondering if you can flip images directly in the shader?

Here is the code:

 Shader "Environment Map" {
 
 Properties {
     _Cube ("Cubemap", CUBE) = "" {}
 }
 
 SubShader { 
     Cull front
     Pass {
         CGPROGRAM
         struct v2f {
             float4 position_clip: SV_POSITION;
             float3 position_local: TEXCOORD0;
         };
 
         #pragma vertex main_vertex
         v2f main_vertex(float4 position: position) {
             v2f v2f;
             v2f.position_clip = mul(UNITY_MATRIX_MVP, position);
             v2f.position_local = position;
             return v2f;
             
 
         }
         
         #pragma fragment main_fragment
         samplerCUBE _Cube;        
         half4 main_fragment(v2f v2f): COLOR {
             return texCUBE(_Cube, v2f.position_local);
         }
 
         ENDCG
     } 
 }
 
 }

Any help much appreciated.