A couple of points Big Red 'L':
Online gaming does not require particularly high bandwidth - a ~500Kbps connection is more than sufficient, what IS required is high SPEED, and rather strangely you need broadband for decent gaming because it is faster and more reliable.
I only have experience of NTL for dial up and tv - all I would say is IMHO they are one of the most useless and incompetent companies I have ever encountered. Avoid like the plague (and I don't work for a telco company).
Regards
Fat Dog