Gosh chaps, I really am most grateful for all your help - just need a better brain to understand it!
Update ... Have, at last managed to login to the router
Helps enormously if the password is entered correctly!!! Anyway, have completed a reset plus resetting the networking setup and the result is - zilch. The only new thing is that when I try to connect to the Plusnet wireless net (which is visible and strongly received) is a message something like "Windows is unable to find a certificate to allow you to connect to this network" or some such. Have no idea what this means ... any suggestions, please?