Do you have the SH2 version of the Plusnet router or the older HH5?
Bear in mind that the BT UPS is available in two versions, one for a FTTP ONT & one for the SH2. Both are identical bar the DC output cable. The SH2 for some reason uses an obscure DC power socket. So If you have the HH5, the SH2 cable won't fit. I've no idea if the ONT one would, so it's something to be aware of.
Thanks for the reply.
I have the Plusnet Hub 2, which is effectively a BT SH2.
I also have my old BT SH2 still, (hence the "spare" power supply), as BT didn't ask for it back when I moved to Plusnet a few years ago.
Always good to have a spare! 😀
I don’t know whether it would be the same in this case but, if it helps, I do know the dc plug on the SH2 is the same as the one on the Home Hub 5a. (Note, the type A. The type B was different).