Had a door mirror glass knocked out at the weekend, glass fine but a plastic clip snapped on the back so would not pop back and stay

Went to Beadles this morning and bought new glass (£39), tried to fit it but the would not go on, did not want to push too hard and break it. Popped back to the parts counter who sent me to the service desk to ask advice, they took my keys and said take a seat, 3-4 minutes later the car was parked outside all done, have a nice day sir.

Can't fault that  09 FL2 HSE auto Lago Grey
71 Triumph Stag 3L
68 NGTCV8 3.5L