Ah, I wondered what those flaps were inside the back box, didn't realise you had to twist them, thanks Walter. I might have another look at the 85mm grey plastic box outside the house, its square, and the underground wire goes into it mostly covered by conduit, but about a 1cm is exposed and those wires (4, I'm guessing current and a spare phone line) are really thin, surprised that snow and stuff hasn't ruined them. When I unscrewed the rusty screw on the grey box the other day it was full of spider web, I suppose because it hasn't been touched for 25 years! Didn't get a good look though, that would show whats on the other side of the back box.
Is the ADSLNATION XTE2005 better than the Pressac NTE2005?