Hours changing after office relocation: ask the expert

I work on a local paper. We were told last week that our office will relocate at the end of the month to a site far away. As a working mum I will find it very difficult to get my children to school and nursery and then to work and pick them up. On top of that, I have been on a six-month contract to work part time (three days a week) and I have been told that this will revert back to full time. My boss has said that he is keen to keep me on the team, and there’s a possibility I can work from home four days a week and go into the office just one day a week. I really appreciate this, but wonder if I have any legal redress as to keeping the part time hours, perhaps if I say that I am unable to secure childcare at the nursery on the two extra days? Working full time I feel is unsustainable and I am keen to keep the hours that I do, or at least to just work four days a week.