My son borrowed my 2008 FL2 today with 99K miles and came back with a story that whilst driving the clutch went right down at one point and stayed there (he had to put his foot under it to bring it back up) and then the bite point felt different. He also wasn't sure but thought that the brake pedal moved slightly when the clutch was down. This happened once and after that all was OK. I just drove it and it felt normal.

Any suggestions? brake fluid level looks OK an no sign of leaks anywhere.

Look here;

http://www.freel2.com/forum/topic19088.html?highlight=clutch

How easy is it to check the master cylinder?

More likely to be Slave cylinder and not easy to check as it's in the gearbox. So gearbox out job 2014 SE Loire Blue SD4 Auto (MY15)
Gone - 2011 GS Baltic Blue, Retrofit Electric Leather, Side Steps, 19"SC's, Roof Rails, TT Sat Nav Mod, Retrofit Premium Audio, Retro fit 2013 Xenons with DRL & Sig Strip (Clutch at 47k)
Gone - 2007 GS Narvik Black, Privacy Glass, 19" SC's, Side Steps,Roof Rails, Roof Spoiler, Lamp Guards, Retrofit Electric Leather (Clutch at 115k)
Gone - 2007 SE Santorini Black (Clutch at 120k)
BT IID (best money ever spent on a car)

I had the same thing, pedal to the floor and eventually no bite at all. Dealer had several stabs at fixing it before finally replacing the slave. Now that I know it's a gearbox out job I can see why they dithered. All under warranty and I got a RRS as a loaner so overall it wasn't too much of a drama in my case. 2020 Defender D200 110S Pangea Green
Gone: 2018 L550, TD4 SE Tech Auto, Carpathian Grey
Gone: Defender 90 200Tdi, Grey Raptor
Gone: 2012 FL2, TD4 GS Manual, Santorini Black