Yes, the landlord can refuse that or any other alteration unless its to do with gas or electricity safety or similar. Social services won’t install without confirmation from the owner of the residence that its okay to install and where the owner isn’t the resident, then they will need written permission, also they may ask for written conformation that the resident is the owner. RATTER is right that the landlord can add provisos, they may not always add the proviso about length of rental agreement but they could, also they could require the renter (or their representative including executor) to agree to be responsible for removal of the stairlift and any making good and/or responsibility for any damage caused by installation and use. I used to work in the NHS, stairlifts was one of the things I used to get involved in.