Phoned moved due to BT copper going (now gone)

[Mike Watterson]

So the question is can the 'line cord for the master be extended down to the hall so I can locate the used items back where they were?

They only rent the name from Virgin. It's UPC/Liberty Global.

But yes, you can run maybe 1km of Cat5.
It only needs Cat3!

I've only had copper for 3 years between 2005 and now.

Even speaker wire, bell wire or alarm wire will work at that distance. The socket(s) (ATA or POTS port) on the cable modem/router simulate the signals provided by a telephone exchange or PABX.