Could someone enlighten me as to what the pipes for running control lines under and through the thwart are made of (Polypropylene, polyethylene?) and suggestions for where a metre of whatever it is could be acquired?

Many thanks in advance
Mark

From recollection I used  FLEXIBLE NYLON PNEUMATIC TUBING AIRLINE PIPE from eBay, 10mm o/d with 8mm i/d it’s quite cheap.

Thank you, managed to get my hands on some, exactly what was needed.