NEWS FLASH!
Just got off my lazy arse and took 5 minutes to measure the PCVhose piece myself.
Turns out my vehicle (2012, 2.2tdci) had a 19mm ID hose between the valve cover and the post-filter intake hose. Specifically, measured where it joins the intake piping. Surely the hose doesn't taper to different sizing on each end? Pic below shows closer to 20mm, but I was balancing ruler, hose and camera all with 2 hands. Hose barb on intake is confirmed 19mm too.
I didn't disassemble further, but there is some crazy looking spring/hose clamp on the engine side, and possibly a male-male barb joiner on the intake side. So maybe the joiner on the intake hose is Male/male 19mm>16mm?
https://www.aulro.com/afvb/images/im...017/01/935.jpg
https://www.aulro.com/afvb/images/im...017/01/936.jpg
https://www.aulro.com/afvb/images/im...017/01/937.jpg
I also have bugger-all room to fit a catch can in the position between the brake master and the intake pipe. I have foolishly mounted my winch solenoid and remote control module there :/
Could mount closer to the exhaust near the coolant expansion tank, but the provent is only good for up to 120celsius... might be pushing it right above the Cat converter.

