Hi,
There doesn't seem to be many answers to getting a BT Vision box working after leaving BT so I thought I'd add a simple solution that may work for people with a mate using BT Broadband and BT Vision working on it.
I left BT broadband and when my BT VIsion box rebooted (after about 30 days) it wouldn't get beyond a error screen trying to locate an internet connection.
However I have found a simple work around which involved taking my BT Vision box round to a mates house who had a working BT Vision service. I simply plugged it in at my mate's house and let it do it's updates then when I brought it home again, I was able to skip another upgrade screen (i selected the 'remind me in 3 hours' option). I also had to skip the initial scan for TV channels screen by selecting the 'BT Vision' button and immediately got the full menus back again.
So far (about 2 weeks later) the BT vision box has been working with no problem using a different broadband provider. Stuff like I-player works, I can also record and watch previous recordings again. I just must remember not to turn the power off. Standby seemed to work ok.
So, if you know someone with BT VIsion then see if you can give your old Vision box a jump start again.
Hope this helps someone. I know it doesn't solve how to hack it problems and get it working independently but it might just allow people to use their BT VIsion boxes for a little longer.