Thanks Saab Dastard,
I have checked the account properties, and nothing appears to have changed from what they were before.
Incoming mail server is a is a pop3 server.
Incoming mail (pop3) is mail.btopenworld.com
Outgoing mail (smtp) is mail.btopenworld.com
Account name and password boxes are completed and the tick is in the box to remember the password.
Gahhh
My apologies for being so poo at computing!
Brian