Afraid my core has finally given up its motherboard or PSU.... sadly in the middle of testing the latest snapshot of 1204. so until I get those sorted, I can't be of further help.
However, just to report back--
It may be just me, but I had the issue again of no internet during install. Right at the beginning when the system checks if there is sufficient hard drive space and internet. Again, I quit the installation and allowed the desktop to come up and then checked for the problem.
This time it wasn't DNS (like last time) but was rather that the interfaces (NICs) weren't configured at all. ifconfig only showed l0 interface.
ifconfig -a showed all 3 so I edit /etc/network/interfaces and added a line for eth0 and then brought eth0 up. Thereafter I was able to run the install from the desktop and, as far as I got, things all looked good.
lines added to /etc/network/interfaces:
auto eth0 inet dhcp
bring eth0 up:
Hope this helps someone if it wasn't a problem restricted to my hardware.