flashasp was absolutely right, it was just this silly me getting the PlusNet details wrong all along - I was putting just my username instead of email@example.com!
(The details I was given 2 years ago said just username for login though...)
flashasp, thank you very very very much for your help. I was nearly sending the router back to the manufacturer and make a right fool out of myself
admin5164, thank you very much for your kind offer to help. I really appreciate it and glad that I didn't have to take up your time because of my small brain.
solstans, thanks for taking time to check the configuration - mine is looking just like yours now and working fine!