If they re-submitted an old DD mandate they must have done so knowing you had cancelled.
Don't dither, this may be fraud, a court can decide. TELL YOUR LOCAL TRADING STANDARDS OFFICE AND THE POLICE WITHOUT DELAY.
And I bet some of those emails did not state their full company name (Tiscali UK Ltd) , company number, registered business address and place of registration. They must put that information in ALL emails, failure to do so is a breach of the Companies Act 2006. Again, complain to Trading Standards.