Unfortunately nothing you can do. Someone out in the internet world is sending out spam messages and forging the details to make them appear as if they were you - hence yuo get the hassle of the 'delivery failures' and aggravated people.
It's extremely unlikely that the emails are going anywhere near your NTL mail system, so there's nothing they can do either.
Usually after a day or two the emails tend to die down and then stop - but it probably won't be the last time it happens
I usually get about one 'attack' a month from one of my business email addresses - it's just a pain to deal with it....