I'm finding this an interesting topic. We're about to put our floor down with the under floor heating integrated into it. Due to space constraints (height), I was going to use 10mm copper to keep the floor low profile (20mm wedi board inlaid with copper, 12mm ply, 8mm engineering AC4 waterproof flooring). Compression fittings are easy to use, and would all be above floor level. All under floor loops would be single piece.
Should I be looking to change to plastic plumbing? Are the fittings options plentiful and easily available? I need to make up a manifold for the under floor heating.