Dear Rabbi Simon
We plan to stay in a rented cottage in Devon. Is it OK to use their toaster if we put it on once with nothing in?
Sorry I cannot endorse using the toaster in a holiday rental. Very difficult to clean thoroughly and the bread comes into direct contact with the interior of the toaster.
A toaster oven however can be kashered through thorough cleaning with an abrasive cleansing agent and leaving it on for 45 minutes. Same as a regular oven. Still best to avoid contact of your food with the actual surface of the oven. Use aluminium foil or similar.
Rabbi Rashi Simon