Thank you for the suggestion. I've tried all I can to remove existing keys. Do Putty, WinSCP and OpenSSH (Win 10) all keep the local key info in the same place (I'm doubtful)? I'm having the same problem despite my efforts (mostly with a fair bit of Google help).

Any further guidance would be most appreciated. I'm no expert on SSH, however I'm a quick learner. :-)

Rgds, Steve.