After finding no helpful info about this I destroyed my wing mirror assembly which I had to replace to see how it was put together! Great news, the mirror glass assembly just unclips from the back of the motor. Be careful, their are 2 wires clipped to it for the demist. don't break them, they just pull off the tags fixed to the back of the mirror. Refit by just clipping your new glass back on! See the photos I have attached! (Unable to attach photo - sorry)