Neat work there. Did you consider allowing for expansion in the copper pipes? I've seen soldered fittings fail after a few years on long straight copper pipe runs where floor chases were filled with sand and cement. I'm not sure how this is best prevented, though.
Pipes usually buried in screed or other materials are always usually fine if wrapped. I've only seen copper fail if it's not protected. I would recommend always using a very weak dry mix when back filling. Thanks 👍
