Parent care/time off work

Hi.

My Father has cancer and is receiving on going operations, treatment assessments etc.

I work full-time and my sister has two young children so difficult for her to help.

She can do appointments at local hospital but I have to go to thr Royal Brompton in London with him.

It's getting to the stage where i'm having to take unpaid leave, and although I don't mind doing this, money is short and wondered if there was any help out there?

Thanks in advance.

Jenny x