It's a low tech solution for the couple who can't find peace at night. Got a partner who hogs all the sheets and leaves you cold? Or how about one who latches onto you trying to find warmth? The half percale, half fleece split sheets set is really sort of two sheets sewn together, with lightweight fleece for those who like it cold and heavier percale for the hotties.
While your bed might normally be a battlefield when it comes to finding comfort, it sounds like the hot and cold sheet set will create a pretty steady wall of temperature preference between you and your partner. In that case, why don't you just push those two twin beds away from one another, Lucy? If you really want to go through with this, a $90 set fits a queen and the $100 is for the kings.