How do i change my brake light switch?

i have a K reg astra estate but cant quite get to the brake light switch.is there an easier way to fit it?|||the switch will be on the Master cylinder if that is truly your problem you just have to locate it and remove anything that%26#039;s in your way and replace it|||Are you 100% sure thats the problem? Thay usually dont fail. If it is the problem then you have to change it. I assume its behind the brake pedal.