Hello, thanks for your question. My name is Tony, I can answer this for you.
A failure to make appropriate and necessary physical adjustments to property can be enforced in the county court. You would make a claim using an N1 Claim Form, which you issue in the county court.
It's much the same procedure as if you were bringing a claim for trespass or something like that.
The action is permitted under s.25 of the Disability Discrimination Act 1995.
Here is the legislation that permits this: http://www.legislation.gov.uk/ukpga/1995/50/section/25
This is the claim form that you would need: http://hmctsformfinder.justice.gov.uk/HMCTS/GetForm.do?court_forms_id=338
It's always worth getting a solicitor to do this for you if you can, they would be familiar with the system and would put things in a way that is likely to deal with this as quickly as possible for you.