I got 'enp0s26f7u1'. The full output from 'ifconfig' was

enp0s26f7u1 Link encap:Ethernet HWaddr 02:0c:e7:0b:01:02
          inet addr:192.168.9.136 Bcast:192.168.9.255 Mask:255.255.255.0
          inet6 addr: fe80::2428:cfe8:7c87:431a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:12822 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9030 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:4353887 (4.3 MB) TX bytes:1929462 (1.9 MB)

enp2s0    Link encap:Ethernet HWaddr 00:25:11:59:cc:58
          UP BROADCAST MULTICAST MTU:1500 Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
          Interrupt:19

lo       Link encap:Local Loopback
          inet addr:127.0.0.1 Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING MTU:65536 Metric:1
          RX packets:1783 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1783 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1
          RX bytes:185895 (185.8 KB) TX bytes:185895 (185.8 KB)

'enp2s0' looks like it was my old land-line modem.

The last number of enp0s26f7u1 changes if I plug into a different USB socket.

Oh, and the £39 in my previous post was a typo. It should have read should have read £30.