In reply to itsThere:
cheapest solution
Re fill an empty spray container (you know your typical household sprays) with one quarter neat bleach (you can buy it for 59p etc.) top up with water shake and away you go, kills mould and bleaches at same time but only for so long.
It's hard at this time of year when it's cold and damp, venting the area is key but it difficult without leaving a window wide open and the bathroom door to increase the airflow especially if you are trying to keep the rest of the house warm!