This was an older stumped house. The way I did it was to remove a power point, look in the wall cavity for where the cable came up out of the floor in the cavity space, and then assuming there was no obstruction, I then got under the floor and drilled up. In most cases I was able to stay a good 20cm or so away from the power cable. Worked a charm. I was paranoid if I got it wrong I’d be drilling right up through the actual floor.

Nowadays, doing the same at my own house… Cut the plaster. Run cable. Patch plaster. No stuffing around with the slowly slowly approach 🤷‍♂️