OK so reading the old threads on BH re insulated pipes, there seem to be two camps:

1. Roll your own. Copper or plastic pipe (maybe 22 copper, 28mm plastic/pex). Insulate with grey PE sponge (or even Armaflex) / air tight foam / eps/xps sheet etc. Even EPS beads if you can keep them watertight. Plus a bit of UV protection. Heat loss a bit unknown but I guess can be calculated. Cheaper (mostly except for thick Armaflex) but maybe a bit prone to problems unless done v. carefully.

2. Buy an expensive multipipe pipe product designed especially for the purpose. Maybe Calpex or Rehau (preferred according to one Build hubber) or Uponor / Isoflow / Hiline / Primary Pro. Either multiple single insulated, dual or fancy multi-pipe including power & data. Interestingly, some of these suppliers don't seem to supply U-Values, which is a bit disconcerting. This option seems to run from pricey to eye-wateringly expensive, but maybe less error-prone.

   Why do I ask? Because I need to specify seals right now (which means I need the number, diameter and smooth/corrugated nature of the pipe). This for the as-yet unspecified pipe running to a fairly undetermined place 😆. Probably for a Panasonic Aquarea J in 5 or 7kW. Location could be about 7m away or much further (20+m) - it all depends on how much my noise-sensitive wife reacts to the noise from a friend's HP next weekend.

   What's the up-to-date hive-mind's thinking on this subject?

Our fat (insulated) pipe is circa 25m from heat pump to manifold.

In the end it was all part of the price for the whole install, however when we looked at the cost it was somewhere (depending on brand/source) between 1.7 and 2.3k which in the scheme of things for a "known" outcome.......

Wasn't convinced the pre made stuff had a great U value and was stupid expensive, so rolled my own. We are about 5m underground and quite a bit over ground via an insulated shed. We used 28mm hep2o and transitioned to copper (28mm) though the wall. Started with 6kW heat pmp down sized to 4kW

We had the 1m run of ours, before it dropped underground, wrapped in a single layer of armflex by original plumber. I then added a few more layers of it, then wrapped it on duct tape. It's reasonably neat, but gives me the satisfaction it's over kill!!