More checking reveals that the 20-setup-apt hook is done after the initial fetching of all the packages. With a bad connection or limited connection this is not a good solution.
Workaround is to configure the mirror's to include the proxy address, and to 'hack' the 20-setup-apt script to use the proxy address for the mirrors as well (since apt-proxy do not go well with the proxy embedded into the mirror URI) -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org