a couple of thoughts:
Cat 6 is a horrible bulky cable nasty to install with large bending radius and not nearly as robust as 5E. Also, hifi techies tell me that it is easier to stream via cat 5 due to imbalances in the cat 6 cable cores. I'd use cat 5, select a sensible point for the patch panel and do phones, pcs and sound/vision from there.
Underfloor heating. Not the screeded type but there are others with tiles laid on top of the pipes, flooring on top (can be wood, tiles etc). This dispenses with a wet trade and mess and the heating has a much quicker response, 4-5 times quicker than screed.
heat pumps go well with underfloor heating but don't use for hot water as efficiency drops. best to use ground source if you have the area outside to bury pipes or if you are rich, boreholes. should get 3-4kW heat output for each kW of input energy.
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