Not sure about the UK. I've seen a lot of outdoor plumbing in Ireland. I lived in a place that had that. They were literally running on the outside. Our maintenance guy said they did that to make maintenance easier, but it also makes wear & tear a lot easier obiously (not to mention frost). And chipboard floors that would crack with heavy furniture. It was terrible quality. These houses were built in the mid 80s.

And a dirty tank of water in the attic to act as a "in-house water tower" because only one tap may be connected directly to the mains. Really archaic.