OK - so it's worth getting a Mk2 faceplate and a decent RJ11 cable. I'll do both those..
I don't want to distract with the HH5-as-a-modem option... I understand it's a stupid idea to have multiple routers on a network but I was just after a short-term workaround. Ideally, I'd like to return the HH5 to BT as a ziplock bag full of its constituent atoms as it has provided me with nothing but stress.that's the ideal scenario.
In theory, the ECI modem should work better (assuming I'm right about the DSLAM being ECI), right? I don't care about hacking the modem unless I can eke some more speed out as a result. Seeing my line stats only induces tears...