At least I have confirmed a cable route I'm planning! Found a couple of cables which go up to the loft inside one of the wardrobes, across to the front of the house, then down beside the stack pipe behind both the showers to a little boxed-in section next to the front door. They are part of the (non-functional) alarm system the house came with and I've confirmed they're the same at both ends by tying some string on where they poke out of the wall in the hall, pulling the wires from the loft, and verifying the string has been partly pulled into the wall. Now I can get some longer string and, while pulling out those redundant wires, I can pull through a cord to let me get whatever cabling I want through in future. First one going in will be ethernet from the study (just next to the front door so it'll be an easy drill-hole from that boxed-in bit) to the loft, down through that wardrobe, out into the loft over the utility room and into the little 6U network cabinet I'm planning to stick on the wall. 🙂 Then there will be another one from the cabinet to a new hole I'll drill in the plasterboard above the stairs to hang a ceiling access point there. Another one to my office (one of the bedrooms repurposed - handily just the other side of the wall from the utility room loft). And probably others! There's a bunch of power sockets I want to add too when I get round to it.