Did some further spade work - the alias is in virtusertable to @www.plainmortgageadvice.co.uk but not without the www. - added it and tried again. Log reports cahnged slightly, looking for a user = alias, rather than user with alias - how the **** does an alias log in!!!!
Code:
Feb 5 13:08:18 sww postfix/cleanup[32644]: 2CE9D21943: message-id=<20080205130818.2CE9D21943@stopwatchweb.co.uk>
Feb 5 13:08:18 sww postfix/qmgr[32620]: 2CE9D21943: from=<www-data@sww.stopwatchweb.co.uk>, size=579, nrcpt=1 (queue active)
Feb 5 13:08:18 sww postfix/local[32646]: 2CE9D21943: to=<formresponse@plainmortgageadvice.co.uk>, relay=local, delay=0.7, delays=0.43/0.1/0/0.17, dsn=5.1.1, status=bounced (unknown user: "formresponse")
Feb 5 13:08:18 sww postfix/cleanup[32644]: AFFC62194B: message-id=<20080205130818.AFFC62194B@stopwatchweb.co.uk>
Feb 5 13:08:18 sww postfix/qmgr[32620]: AFFC62194B: from=<>, size=2365, nrcpt=1 (queue active)
Feb 5 13:08:18 sww postfix/local[32646]: warning: maildir access problem for UID/GID=33/33: create maildir file /var/www/Maildir/tmp/1202216898.P32646.sww.vm.bytemark.co.uk: Permission denied
Feb 5 13:08:18 sww postfix/local[32646]: warning: perhaps you need to create the maildirs in advance
Feb 5 13:08:18 sww postfix/bounce[32648]: 2CE9D21943: sender non-delivery notification: AFFC62194B
Feb 5 13:08:18 sww postfix/qmgr[32620]: 2CE9D21943: removed
Feb 5 13:08:18 sww postfix/local[32646]: AFFC62194B: to=<www-data@sww.stopwatchweb.co.uk>, relay=local, delay=0.16, delays=0.09/0/0/0.07, dsn=5.2.0, status=bounced (maildir delivery failed: create maildir file /var/www/Maildir/tmp/1202216898.P32646.sww.vm.bytemark.co.uk: Permission denied)
Feb 5 13:08:18 sww postfix/qmgr[32620]: AFFC62194B: removed
Can anyone understand this behaviour? Some progress, anyway: at least the domain and alias is now each in its correct right place. Still no email from thesite, though, which is the purpose of the exercise.