(forgot my manners!)
I don't think it is 'you'. I don't know enough about how these 'dynamic DNS' services work, but I do know that some badly-coded web sites assume 'your' IP address is actually the address of the proxy server that NTL force you to go through. It may be that your dynamic DNS service has the same problem, i.e. it is picking up the proxy address rather than your own. 'no-ip' is a well-known (and free) service which MAY not have the same problem. At least worth a try?