So I am presuming that you are currently working a five day week?
It depends what your current situation is? I was reduced from 5 day week to 3 day week and it suited me as I had previously had children in creche full time and so reduced their days to part time and I enjoyed the other 2 days off with them.
As my days were reduced to 3 days I was able to claim job seekers benefit for the days not worked. Job seekers benefit is based on 6 day week, so was claiming for 3 days.
To be honest with me working the 3 days, reducing child care fees I am better off but that is my situation.