Cooked Cottage Pie, refrigerated. How to reheat
180 for 45 minutes should do the trick. Just make sure it is piping hot in the middle before serving.

Cover the dish with foil to prevent the crust getting any crustier. You will still want to take it off for the last ten minutes of cooking to crisp it though, as the foil will make it soggy.

You can absolutely prepare Cottage Pie to the pre-baking stage and fridge (or freezer) it until the next day. You need to cool it relatively quickly though - hot food shouldn't sit around for more than a couple of hours. Place the dish in cool water (obviously not over the lip of the dish) and change the water a couple of times as the pie warms it, then cover and put in the fridge or freezer.