You have to remember, my first VDSL install WAS self-install as it was with Digital Region.
Cabinet connected on a Wednesday, line dead at home. As it was a self-install, engineer did not attend my property to ensure it was connected correctly.
Openreach then refused to accept it was their problem, blamed the DR cabinet. My ISP then spent the rest of the week trying to get an Openreach engineer out, they eventually discovered (by trying to call my land line) my E-side was connected to someone else. By this point it was Friday so nothing got done.
It was only then on Monday when they sent a PSTN engineer to my house that I was able to explain and he used the tone generator to find out where my line was in the cabinet. Turns out, they had actually repaired the womens line who mine had incorrectly been connected to on SATURDAY and left my wire just dangling loose in the cabinet, despite the fact my line fault had been reported first. Because mine was reported as a broadband fault, hers presumably as a PSTN (as she was with TalkTalk), they gave mine a lower priority.
Now granted, as the cabinet is now Openreach also they can't as easily put the blame on someone else. But its clear from past experience and reading online, self-install allows BT to pass the blame for line faults onto the end user and bully them into not wanting to report a fault in case the engineer reports back it was an end-user problem. With an engineer install this should never happen, as they should ensure all wiring before the modem is correct and that the line is fully functional before they close the job.
Now granted, if you are moving from FTTC to FTTC provider, this should be unnecessary. But I still think they should provide a modem so they have accountability up to the ethernet port, even if the end user then uses their combined modem/router. Its something to fall back onto if there are problems. Its far too difficult for an ISP to diagnose problems when every user has completely different hardware. The modem avoids that, as you can always do a manual PPPoE test without any router connected.