[Mesh] Unity 4 to Unity 5 Mesh Export

Hi, i'm having issues with exporting mesh data from Unity 4 to Unity 5 by collecting the MeshFilter.sharedMesh.vertices, MeshFilter.sharedMesh.uv etc.

In editor mode i'm setting arrays in Unity4 for every GO with a MeshFilter (see below). The arrays contains its needed mesh data, the same array is applied to the MeshFilter.sharedMesh in Unity 5 using:

             MeshFilter mf;
             
             if (mf = GetComponent<MeshFilter>())
             {                    
                 mf.sharedMesh.Clear();
                 mf.sharedMesh.vertices = m_Verts;   
                 mf.sharedMesh.uv = m_UV2;
                 mf.sharedMesh.triangles = m_Triangles;
                 mf.sharedMesh.normals = m_Normals;
             }

The mesh itself is re-created fine, however the UVs are always offset incorrectly - as if unity 5's Mesh class expects them in a different order or space?

Does anyone have any insight into this they can share, or been able to successfully copy mesh data from unity4 to 5? Has the Unity 5 Mesh class changed the way it handles UVs that might be the cause?

The reason i'm doing all this is to use the lightmap data and the Auto-Generated UV2's from the Unity4 scenes in Unity5.

Many thanks