2019 Vauxhall ADAM clutch pedal not fully lifting back up

Hi - Can anyone help - seems like a really common problem.
2019 Adam with 12000 miles on the clock. The clutch pedal gradually got lower and lower until impossible to change gear. Lifted pedal up manually and was fine. Gradually pedal gets lower, keep lifting it up and all OK. Garage has had a look and says it needs a new clutch !! It has been driven like this for 9 months now, surely a failing clutch, slave cylinder, master cylinder etc would not last that long without deteriorating ? Garage also said the clutch pedal spring was broken but they say it serves no purpose ?! As this spring is apparently in a sealed pedal box, does anyone know how they could know that ?
Really really would appreciate some ideas answers - please