Assuming the problems that you were having was that your devices could not access your email account the following may help.
There have been problems with the BT IMAP/POP servers stopping email clients from accessing the users email account for years. When this happens the advice from forum users is to do nothing such as changing passwords or deleting and resetting up accounts as this invariably causes more problems than it solves, as unfortunately you have now found out.
If all your devices stopped accessing your email at the same time and you were still able to access your email via webmail (using a web browser) it is obviously not a problem with your email accounts or with your password, hence the advice not to do anything. The problem usually resolves its self in a day or two.
Did you change your password?
Is the password on your iPhone which still accesses your email the "old" password or the "new" password.
If you did change the password, because you have deleted and reset up your email on your devices and changed your password I would suggest that you try the following:
Switch off all your devices or at the least stop them from polling your email account for new email. You can do this by either deleting the email account from the device or just change the email address in your email account settings.
Change your webmail email password yet again.
Wait at least 15/30 minutes before starting one of your devices email app and set up the email account with the new password.
Check that this device is working before moving onto the next device.
Ensure that you are using the correct settings via this link and set the email accounts up manually rather than using the email wizard.
I would recommend that you reset your BT homehub as the possible first remedy.I have a couple of BT email addresses and one of the two refused to be recognised on my iPad and iPhone...ie ‘username or password not recognise’.I changed the password,checked other details to no avail.Switched the homehub off and on,everything fine.