Question Author
Thanks for your answers.
'DX' are the 2 last letters of one of the 6-digit postcode the agents gave me (such as AB1 2DX); it's not a DX address!
Anyway, I'll see how it goes. I've got to call back BT today, I hope they manage to book me an appointment, postcode or not postcode. Have to check with the site manager where the BT box is, and whether it is accessible at all times, or whether I need to have him around when the BT engineer calls.
Back very painful from carrying all those cases and bags and boxes yesterday!
Thanks again.