Thanks for the advice - I will look into it. The socket is indeed the LJ 2/1A but a bit yellow with age! I had already disconnected the ring wire to extensions but a fixed socket would certainly be tidier than a trailing filter.

As an update, my service changed over at 12:00 noon - a couple of hours before the home hub was delivered. The phone went dead for about 10 mins as well. Thus it was useful to set up the old modem and start getting emails working (a word of warning - see below). The modem synced a bit faster (5.7Mb vs ~5Mb before) . The HH3 connected at the same speed and, as far as I can tell, still on ADSL Max (connected G.992.1 Annex A; noise margin ~ 12dB during the day, ~9dB late evening).

One small niggle with BT - having chosen a good password when setting up the user name, I had to change it as they sent it in clear form on a confirmatory email! On 3 different devices I had to alter the SMTP details.

Thanks again - really helpful to get confirmation - better to ask when one can rather than struggle without any internet connection.