For scones can I mix cold butter with self raising flour and then add the wet ingredients the next day. This is to save time in the morning?
I do the same as you, Vivien. I find that mixing in the liquids in advance leads to too much gluten development and some outgassing from the baking powder, but that if the butter/flour mixture is kept cold enough it doesn't hurt to mix it the night before. (Anyway, it takes longer for the oven to heat up than it takes to mix together the remaining ingredients and shape the scones.)
I regularly prep scones completely the night before. As in, I make the entire dough, place on a baking sheet, and put in the fridge until morning. So you can even go a step further and add the wet ingredients too the night before to save even more time in the morning.