I've just booked a holiday for a special birthday and then realised after I booked it that someone else is off in the office. There is 3 people that work in the office and there can only have one person off at any time (obviously different if someone is off sick - lunch cover is provided). The person is off one day over my whole holiday. It would be extremely expensive if I was to change my holiday and the other person won't change it as she's going away for the weekend. Is it reasonable to let two people have the time off together and ask for cover? It's the first time this has happened and we normally work holidays around each other.