Thought I'd post this incase it helps any other poor frustrated NTL BB customers:
I've spent the last 2 days trying to sort my mums new BB connection. I've tried everything I could find on this, and other forums but was still getting a very intermittant connection, usually connected for less than 30 seconds and most of the time could not renew the IP (usually came up with a 169 address).
When nothing worked, I reinstalled XP and tried again - no luck. So I tried settings in the control panels for the network card - still no luck.
Tried pulling the coax connection on the STB - still getting a 169 address or the " Unable to contact your DHCP server " message.
After exhausting all the tricks in my software-sorting bag I had the RJ45 connectors off the wall. I found one cable was barely touching the connector and needed very little encouragement to come away altogether.
Luckily I'm an electrician by trade so posess an IDC tool to re-do the connection. All now works perfectly
As part of my job I've installed hundreds of ethernet boxes, I've never had one report of one being faulty - why? - because it's
not that difficult to do. It just takes the right tool and a bit of care, something the monkeys

that installed my mums cabling were obviously lacking.
What also didn't help was that the tech support guys from NTL are probably told not to suggest that it could be a faulty cable, because they'd be casting doubt over the competance of their own installers. You can't blame them for that I suppose.
To sum-up, firstly thank **** for this forum and for all the people who contribute so much time and energy to it. And
no thanks to the little **** who installed my mums cabling - he owes me 2 days and one sleepless night - go and stand in the corner!
If all else fails - check your cables !
Ewan