Ha ha, on the NTL bill there is NO letterhead with any address, merely the URL for
www.ntlhome !!!! Sounds incredible, but is true!
I noticed a couple of years back that NTL bills changed from normal paper, in colour, with contact details, phone numbers etc, to cheap, black & white recycled looking paper, with no contact details on them. On the back, they have their PO Box addie and the switchboard number, and addresses for the Ombudsmen!