Aptitude with ISO and network repositories?

[Per Dalgas Jakobsen <pdj@knaldgas.dk>]

I'm trying to set up Aptitude with a DVD-ISO and network repositories,
but failing to get it to work.

I'm sitting on a quite narrow network-link and I would like to have
Aptitude fetch package from DVD-ISO if package is present there and up
to date, otherwise from network.
Can this be done, and if so, what am I missing?

:~# cat /etc/fstab (relevant line only)
/var/local/aptitude/debian-6.0.0-amd64-DVD-1.iso \
/var/local/aptitude/mount-point    iso9660    user,loop    0    0

:~# cat /etc/apt/apt.conf.d/00CDMountPoint
Acquire::cdrom::mount "/var/local/aptitude/mount-point";
APT::CDROM::NoMount;

:~# cat /etc/apt/sources.list
deb http://ftp.dk.debian.org/debian/ squeeze main contrib
deb-src http://ftp.dk.debian.org/debian/ squeeze main contrib

deb http://security.debian.org/ squeeze/updates main contrib
deb-src http://security.debian.org/ squeeze/updates main contrib

deb http://ftp.dk.debian.org/debian/ squeeze-updates main contrib
deb-src http://ftp.dk.debian.org/debian/ squeeze-updates main contrib

:~# apt-cdrom -m -d=/var/local/aptitude/mount-point add

:~# aptitude update
(no indication that ISO is included)


I've been browsing around but unable to figure out what I am missing.
I've tried a couple of other things but no success.
Any hints?

~Per