You are sure it is a VDSL Modem/router and not an ADSL modem router? ie your friend used it on a fibre connection without an Openreach modem.
I would agree with licquorice's remarks about HH6. If you are sure that you set everything up correctly with the Plusnet equipment that only leaves a problem with your actual connection and assuming the engineer fixes it, you won't then need to wait for a replacement hub.
Personally I would hold onto the Plusnet equipment if your friend will let you. You may find it better than the "Smarthub".
Just come back from five days of flashing purple. India went through all the script resetting the hub etc to no avail and dispatched a very helpful engineer who arrived yesterday morning. He did all the line tests etc and tracked a fault in our port at the exchange which stopped the hub syncing.
Having moved everything to a new line and reset the cabinet connections purple (eventually) went blue at 29Mb and then snuck up to 46 by evening.
Now to setup the house wifi (once more) as everything changed with the resets!
@kitbooth, the obvious question from that is, why didn't BT's remote diagnostics pick up a fault at the exchange?
It's no good for BT and a misery for its customers when engineering diagnostics are inadequate.
After quite a while of 'diagnostics' it was originally declared a neywork fault and, after escalation, not a network fault but possibly a fault at my property.
You would have thought that a faulty port should have shown up where ever the diagnostics originated!
A strange byproduct of the diagnosis and resetting of the hub has been that the wifi password has reverted to the original! When I had the first of the 'destructive' updates last month it would not let me proceed without changing the password to one different from the original 'preset' on the pull-out card.
Now it has gone back to that and BT wifi in all its wonderful versions is re-enabled.