The mirror has gone faulty within warranty period. I'm not sure why you'd think it wouldn't be covered, it's not a wear and tear item. Surely better to try than pay £60 out of pocket? Plus it's a common and well known issue.
It depends a lot on the cooperation of the dealer, usually they'll just swap it out because it's a small claim but after they tried to reject my door glass claim as a cosmetic fault and not mechanical they tried to claim the mirror was not done under Toyota warranty but as a goodwill from the dealer. Mine was only delamination, not complete failure of the unit. The dealer should swap it out as it has broken.
Add that link to your favourites so you can purchase another one in three years time when it fails again
I had my original mirror replaced under warranty. Had to fight with Toyota because the car was about 4 years old IIRC, and they claimed that the 5 year warranty was actually only a 3 year warranty on the interior :/ A sternly worded email to Toyota UK saw to that and it got replaced.
Earlier this year, that replacement mirror failed. I ended up buying a normal, plastic framed Subaru Impreza mirror off ebay for about 20 quid - https://www.gt86ownersclub.co.uk/for...rror-woes.html
Must say I do miss the bling and the wide angle of the frameless mirror, so maybe when I'm feeling flush I'll buy one from the Toyota ebay store, but it's a bit annoying paying 60 for something that I know isn't going to last.