I didn't see the session dump on the confirm page so had to add it.
one thing i see is that there is no email address for the from address:
["waue_coventry_builder_email_1_From"]=> string(55) "F Geo Robinson - Martyn Blair "
Try using only a from address and do not fill in the from name in the settings.
Some SMTP servers will ignore the from email address if the form name is supplied to, which can cause the email to fail being relayed.
further down in the log, i see the following output:
["waue_coventry_builder_email_1_Log"]=> string(46) "Sending To: firstname.lastname@example.org... Success
this tells me the email is being sent to the SMTP server, it is the SMTP server that is not relaying the email, probably because of the From address.