well from my personal experience…this is typically something that needs to be done by the hosting company…and whenever ive asked if i could get a different ip, the question is always “why”…and if they agree…youll have to wait the propagation time like one would initially do when assigning new name servers to a domain name……and thenagain im not sure how you are operating…so my comments may not apply!
Dom, your registrar has nothing to do with IP’s… thats strictly a hosting issue. They must assign the IP to the domain, and update their NameServer to reflect the change…. Registrar just points the domain at the host.