A quick google search suggests they should be available now. The article specifically talks about the situation your father is in:
https://www.pharmatimes.com/news/nhs_patients_gain_access_to....
>Initially, Ronapreve will be targeted at hospitalised patients who have not mounted an antibody response against COVID-19.
>This includes individuals who are immunocompromised, such as patients with certain cancer or autoimmune diseases.