As others have indicated, simply using a residential address as the registered office of a limited company doesn't mean that you'll pay business rates.
If any part of the residence is used as an office (or for other business purposes) you should read this:
http://www.voa.gov.uk/council_tax/working_from _home.htm
(In particular, click on the 'View examples' link to get an idea of when the Valuation Office thinks that it would be appropriate to charge business rates).
Chris