Scirocco Central

I have a 13-plate 1.4TSi and having a problem with the clutch pedal - I wondered if anyone can advise?
About a month ago the bite point slowly dropped until the pedal was on the floor and the clutch was permanently engaged. My friendly local mechanic showed how you could pull it with your hand and it popped back up. He took it away and swapped first the slave cylinder, then when it kept doing it, the master cylinder. It still kept doing it, so he tried swapping the slave again in case he'd fitted a dodgy one. It's still doing it - about every day or every 10 miles the pedal works its way down. There's also a squeak from the clutch itself as I move the pedal around the bite point - but I'm not sure if that has anything to do with it.

My mechanic says there's no fluid being lost, and suspects air getting in, but is struggling to work out what the problem is. I wondered if anyone has had a similar problem or can advise?

It does have all the symptoms of a clutch master cylinder. If air is getting in it must be via the pipe work or joints but I’d assume you’d experience some fluid loss as well, however the loss maybe so little it may not being seen on the levels. Are you bleeding by pumping the pedal or by using an easy bleed or something similar? If it’s only by pumping the pedal it may be worth trying an easy bleed kit and replacing a substantial amount to ensure every bit of air is expelled from the system.
Have a good look at all of the pipes / joints as there may still be a leak but it’s not being noticed in the levels.
Hope this helps