Wouldn't it be more worrying if your PC
wasn't talking to your router?
I'm not an expert on these things (wait for RDHW if you want one

), but as I understand it your PC will send broadcast messages to all other computers on the network every so often, just to see who's out there (for Windows file sharing, and so on).
It's perfectly normal behavior, and nothing to worry about.
As for DNS, what server does the PC have as DNS servers? If it's the address of your router (probably 192.168.0.1), then try changing them to:
194.168.4.100
194.168.8.100
These are NTL's DNS servers, and will then bypass the router for DNS requests.