Here in the states, if you have a Home Depot, they make some pretty easy lines to use for doing a darkroom, it got a bad rap a few years ago when it was being used for stuff it was not designed for, it is called quest and I have done a couple of darkroom plumbing setups with it and it works great, very easy to splice into existin plumbing as everthing is either screw together or crip fit, and really pretty cheap, won't really break in freezing weather and holds all the pressure that most applications require, I just plumbed the new shop for doing glass with it and spent less than $100 to do it and the shop sits about 50 feet from the house.

Dave Parker
Satin Snow(TM) Ground Glass