Work or sick pay

I need some advice please. My husband has been diagnosed in jan at 44. He works as cleaner for 40 hrs weekly. He told his boss he wants to return to work and asked for occupational health. He is now in a state and not ready by all means to set a return date yet . Has sick pay entitlements . Don’t know what advice anymore if best to remain in sick leave longer or ask for phased return knowing that he won’t be able to do full hrs. What would you do?