Thanks all for replying. (I have PM'd Adam).
The installation was done by a contractor rather than an openreach engineer. (I can't recall what was on their van, but was something like Kellys or Quin).
The guy was several hours late and not sure if that impacted his day, but the old master socket was in the hallway, and unsuitable and so I asked if the new master socket with faceplate could be fitted in an adjacent room. There was existing phone cable to another socket in this other room, and so he "bypassed" the existing master socket and placed the new plate in the other room, next to suitable sockets etc.
He said he had problems with the phone line, but the broadband was OK. I couldn't test connection as I didn't have a router from PN at the time. I've now had this service and speed for a week, and it has been consistent at that speed.
Thanks for your help and input.