"T i m" wrote
| I should have taken note of the make / model on the existing handsets
| shouldn't I ;-(

Yes, and until you do we're not really much further forward.

| The BPT one looks like it might do (subject to the technical stuff) ..

If it's a BPT (or is it BTP I can't remember offhand) panel and speech unit,
and power supply ...

| ? Do these things normally come with a line cord or are they hard
| wired?

Hard wired. BPT and I think Entryphone provide adapter bases that can be
used on a cord.

| I can now also add there are also separate12V DC and / 12V AC supplies
| to this system (DC for door entry mech / phones / panel, AC for
| camera?).

More likely DC for panel speech and camera, AC for the lock or some systems
use AC buzzers in the handsets.

Owain