The BT smart hub isn't as good as it seems (IMHO). I've no experience with what Plusnet supply but if your not happy with it I'd go for a seperate modem, HG612 or a Zyxel set up as modem only perhaps, and a router of your choice. Then you can use the same kit whatever ISP you choose.
I'm actually on BT myself since September but don't use the supplied hub. One reason is the ease of getting stats out of it so you can monitor how your line is performing.
Sent from my Nexus 6P using Tapatalk