Your Local Authority has general powers to improve living conditions in its area, and these may include the repair, improvement and adaptation of housing. It will have a published policy on how it uses these powers, available for instance at public libraries.
Local Authority assistance for these purposes can be in any form: loans, grants, in-kind or simply advice, and will vary according to the area in which you live. If you or someone in your household is disabled, you may qualify for a mandatory Disabled Facilities Grant (DFG).
The following help sheet explains in full what a Disabled Facility Grant is, how it is calculated, applying for the grant and what it can be used for, to guide you through the whole process.