Thanks for this advice - does the outer mirror casing come apart to give access to this?It could be the glass come loose. Or it could be one or more of the 4 clips that hold it to the internal part of the door mirror assembly. You can't ever be sure what damage/unwanted attention it has received when parked to cause that.
Either way I would take the glass/backing plate off and assess. You need to get a screwdriver right under there and lever from the point of connection. NOT the edge of the glass - you'll guess what will happen.
No. It's the other way round - remove the glass to take the casing apart.Thanks for this advice - does the outer mirror casing come apart to give access to this?