When Quinn's "engineer" fitted my FTTC he had to do a remote line test via his mobile - sub-contractors aren't issued with the BT test equipment. He had to try 14 times before he got a successful test... :P
He wasn't in a hurry to install the modem, either - asked to see my router, so presumably they are geared up to only plug in the BT Home Hub 5, so I didn't show mine to him, instead he saw my HH4 which doesn't have the built-in VDSL modem, so he went and got a modem off his van and plugged that in instead. I then moved the modem to the other end of my pre-existing data extension cable, and plugged my TP-Link router in to that. Connection has been stable as anything, but much slower than it should be.
I've currently got a speed fault logged - I have only seen one green BTw test since the installation.