There's obviously nothing in employment law about the right to watch live sport. All employees with 26 weeks' service have the right to make a flexible working request for any reason. But this kind of request can only be made once a year, and anyway is not really designed for one-off events like a sporting event.
However, you do have certain rights around when you take your annual leave.
Your boss has to allow you to take all your leave during the relevant leave year. They can specify in advance particular dates on which you're not allowed to take leave. Check your staff handbook for the rules about this, but if the rules are silent, your employer must give you at least double the amount of advance notice as the length of time over which leave is banned.
