Provided that my sponsor owns a house in the UK, are council tax and utility bills enough documents as proof that my sponsor can accommodate me?
GOV.UK provides guidance about documentation to support a visa application. Note in particular All documents must be originals and not photocopies and Section 4:
Section 4: documents you should not send unless specifically requested
This page provides guidance on the types of documents that are not required to consider your application.
• if you are applying as a family/group you do not need to provide multiple copies of the same documents
• bank statements or letters issued more than 1 year before the date of application
• driving licence
• photographs (other than passport photographs required in section 1)
• notarial certificates
• business cards
• hotel bookings
• flight bookings
• photocopies of bank cards
• credit card statements
• certificates relating to leisure activities
• evidence of car ownership
• travel insurance
• sponsor’s utility bills
• sponsor’s council tax bills
• educational certificates (unless specifically listed in section 3)
I have emboldened the two you ask about.
Section 2: other documents you may want to provide – all visitors covers what may strengthen your case. This includes, from sponsors:
where a third party (who is either in the UK or who will be legally in the UK at the time of your visit) is providing financial support to you e.g. a business, a friend or a relative, documents to show they have sufficient resources to support you in addition to themselves and any dependant family should be provided