To ask to expense the nursery fee

[neverwakeasleepingbaby]

The company I work for organised a training day which I said I could attend, but then it was rearranged to one of my non-working days due to the trainer being ill.

I don't necessarily have a problem with "working" on one of my non-working days (since it is CPD) but I don't have any childcare on that day.

I could ask one of the grandparents to look after DS, but they live quite far away and I don't feel as though they should have to. The other options are DH takes annual leave (again, a loss to him). Or, I could put DS in nursery. But that's an extra £72 for us to pay.

Would it be unreasonable to ask work if I could expense the nursery fee? Or is this extremely cheeky?

Thanks for all your replies. Just to update, I've discussed this with my boss and HR, and they've agreed to cover the cost of nursery only. I did ask to be paid in full but I guess this is a compromise that doesn't leave me out of pocket. Not totally happy that I'm basically working for free but it's only a training day so it's not too arduous!