I tried tracing what seemed to be the wire, it went to a box that has been ripped off and from there I couldn't really tell.
I also plugged a landline phone into the socket and it worked and let me make calls so I assume this is good news and that the internet will be fine once it's switched on.
I've also asked the people we bought it from where the master socket is but no reply yet.
Jesus, yes that looks like a BT 3 pair.