Are you able to access your email account via webmail, for example GMAIL can be accessed at www.gmail.com can you do likewise for your email provider, if so test your credentials on the site, if they work there they should work on your iPad.
Provider is Virgin media (blueyonder.co.uk) - Yes, can access mail through their webmail OK.
But mail on Mac will not access - just gives message "Blueyonder IMAP server - imap4.blueyonder.co.uk rejected password for user gill.lloyd108". Up to yesterday all was well so no idea why this happened, etc.......
This is going back a while but I remember there were specific settings for email to work on iPhone/iPad etc, so this may help as I used to be with Virgin Media.
It looks like you are using IMAP from what you've said, so make sure you follow the details under the IMAP heading.