The boffins must have tweaked the network overnight because at 1000 here I am with the fastest connection I have had since I had the NTL600 installed.
The internet speedometer on Norton System Doctor is pointing towards 2 o'clock or lower instead of the 10 to 11 o'clock during the rare times I had a connection over the past two weeks.
So far so good. I might even start praising NTL Broadband if the connection continues like this.