If you move to PlusNet they should provide a (feeble but adequate) router and Openreach should supply a modem. (Those rules may well change later.)
You would then have the choice of using just HH5 as modem/router as you probably do now, Openreach modem + HH5 as router, or Openreach modem + PlusNet router.
Just HH5 is easiest and has just one device running, but some people find it does not give as good a VDSL connection as the Openreach modem. If you are satisfied with they way it behaves as a modem on BT, it will still be exactly the same on PlusNet.
I had Openreach modem + HH3 when I moved. I kept that configuration as it saved bothering with any new wireless configuration. I think the HH3 and my (previous version) PlusNet router are probably about equally feeble, but quite adequate for me. Unless you are feeling very philanthropic, turn off the BT Fon on your HH5 if you had it on for BT.
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Recently moved from BT Infinity 2 to PlusNet. Very happy so far.
Edited by StephenTodd (Tue 27-Jan-15 18:10:56)