I have retrofitted folding wing mirrors ,
You will need properly to change the door modules, even my Sline car had to change modules.
You need to replace you wing mirrors with folding units, ( can be hard to find now)
and replace the drivers door switch console with a folding option.
I used Door modules from a Seat Exeo, used from Ebay.
Finding replacement folding mirrors could be difficult, looked on Ebay yesterday and found only 2, one was priced at £160.
Used a drivers console from a Seat Exeo, same as B7 but newer condition.
The good news you do not need to programme them, just fit and go.