Just going to update this for the sake of anyone googling a similar issue in the future. This post doesn't contain any questions/info relevant to the previous posters ITT, so you may want to skip
Since the BT tracker didn't acknowledge the need for an external fix, I called up today. 08005874787 didn't directly work, for some reason- had to go via India and get transferred back. When I did get through, they were very helpful.
I was told that the external work will be done tomorrow, but unexpectedly I was also given a timeslot for another internal visit next week. Turns out someone needs to sign off on the final install. If it's a different engineer from before, I should probably take the opportunity to ask about the staples/connector issues
It will be interesting to see whether the service works from tomorrow, or only after the second internal visit.