Hi Den
Are you working to any terms and conditions on your part? if so then you will have to follow these, which as Martin said should exclude bank hols etc.
If there are no terms and conditions, then it's up to you! decide on what you want to work, or not, over the xmas hols then write to your custards and tell them, just give them 30 days notice...
Think about it from your custards point of view, if you had finished work for the xmas hols, and were at home relaxing, the family is round enjoying the festive season and the door bell rings.... It the cleaner!!
Only my opinion, I try and have as much time off over xmas as possible, a bit of R & R just like everyone else.
We may be cleaners, but we are hard working people as well.

Chris