cable / fibre
Yes / no.
Virgin cable does not require a phone line. Anything else readily available domestically does.
“Fibre” is fibre to the nearest street cabinet (“FttC”) and then delivered over what they call “the last mile” via the phone line. Direct fibre to the premises (“FttP”) exists but it’s hellishly expensive and only really viable for businesses.
which is what I’m after, to make sure people are unable to make calls at my expense
I’m really not sure what you mean by this, can you elaborate? Most phone packages have had free phone calls for a long time, the whole point of not needing a phone line is not having to pay BT / whoever £15-£20 a month for the privilege of having a few metres of wire strung to your house. Who do you think is going to be making calls?
I have “fibre” ADSL over the phone line via Sky. My actual phone stopped working 2 or 3 years ago, I used it so little that I couldn’t be arsed to report it.