Do you still have the router you were using with BT?  If so, what router is it?  It should be possible to use your old router on your Plusnet service - this may solve the problems you are experiencing.

[Edit - typing errors]

I am guessing its not the HH5, but if it is, then as above just use that.
There are a few things that you could try though, make sure smart setup is switched off, also consider un-syncing the 2.4 and 5G wifi channels, add 5 to the SSID of the 5G one so you know what you are connecting to.
By the way, welcome to the forum, stick around it is a great source of helpful tips.

Quote from: geofftheref

Switched from BT to PlusNet on Saturday. Wifi printer now not working. Advised by Epson that it is a router problem - undoubtedly as it was working fine before. Ten minutes in queue for support to be told "not our problem we don't give printer support". If this is the shape of PlusNet then its going to be a very long twelve months.

In all fairness i dont see any problems with them saying " we don't give printer support "  its really down to you to manage your own printer. If you are unsure about anything then always ask in the forums... theres many here that will help you.