My fault. The glass is intact and still attached, but has sprung out. My grandson has wedged the glass in place temporarily.

Thing is, how do I set it permanently, or will I have to take to the garage for repair?  Mirror is unheated.

 

How difficult will it be?

You almost certainly need to replace the entire wing mirror because there will be internal damage that you can't see. 

On the back of the mirror glass is a circular plastic device with several small clips. In the mirror housing is a circular head either mechanically or electrically worked which moves the mirror. The clips on the back of the mirror are a push fit over this circular head. If the clips are intact and the guts of the housing not broken then careful lining up and a firm push should re-seat it. It is glass so try to push evenly all over the centre circle area or it may crack. If the mirror adjustment device is hanging out with the mirror still attached then as above. New complete unit time. Should get one for under 30 on ebay.

Edited 3 October, 20196 yr by LB123