For most of us, when we pass, we'll basically have to pick between burial or cremation — and if you want a plot, you generally have to pick it out early. Sure, there are other options out there, like having your remains composted, or donating your body to science, but the vast majority of us will go with the more traditional methods. It's all a personal choice, and one of the most personal choices you'll ever make.
For Britain's Royal Family, well, things tend to be planned out ahead of time, and they have little choice in the matter.