If you are a sole trader i.e. not registered at Companies House, and are self employed you will NOT need to have a registered address service. HMRC will need your address, but this is usually either your actual physical place of work or your home address. This is not publically available.
Registered office services only apply to limited companies, CIC's and LLPs.
As a sole trader you may not want to publicise your home address so you may wish to consider using our mail forwarding service, which will forward all your mail directly to you.