You've got the information in your post correct sfaik.
BT supply the HH5 which is a combined modem / router. Either the modem supports ADSL and VDSL (Infinity/FTTC) or there are two modems - I don't have one and don't know the details.
On Plusnet FTTC I got an Openreach modem and opted to use my own router. Neither the old nor new Plusnet router has an inbuilt VDSL modem so if you switched to Plusnet you'd need either an Openreach modem + a router or a combined VDSL modem/router which Plusnet don't supply. How they'd provide that I have no idea unless they arranged for an engineer install which would otherwise not be required as you are already connected to your local fibre street cabinet.
My bet would be they would arrange the engineer install though.
Edited by kwikbreaks (Tue 27-Jan-15 16:24:30)