Do I need to split the title?

I recently purchased a building that has an occupied 1st floor two bedroom flat that the tenant is staying in, and below it a self contained set of rooms with their own entrance that have most recently been used for general storage. On the basis there is an old shower & toilet in one of the rooms, I suspect been habitable at some point in the past, although it no longer has any individual electricity, gas or water utilties connected. We would like to renovate the downstairs area into a one bedroom flat for rental. The title of the building is for the building as a whole at one address. If I want to have two seperate addresses for the two flats, do I need to horizontally split the title, or can I just apply to someone (the council?) for creation of a second address for the downstairs property, which will allow me to get the utilities connected again?

Richard - all depends what you mean by rental here. If you mean a short let (less than 7 years) so no lease and more of a rental agreement then that won;t impact the land register
The local authority will deal with any address issues

Adam - many thanks for your swift reply. Yes, it would only be an assured shorthold tenancy agreement for both flats, that would be renewed (if desired by the tenant) annually, or a new tenant would come in. On the basis of your post I shall contact the local authority to see about getting an additional address added instead.