Not to scare you, but when you're moving into a shared accommodation, who knows how many people slept in that bed before you. An Antibacterial Mattress Protector (£16) will give both you and your mum peace of mind when you settle in for your first night away from home. If you find your mattress is sagging or uncomfortable, consider upgrading to a memory foam one for an added layer of comfort.
Top tip: Take a photo of your mattress on the day you move in, so you can argue against any charges for a dirty and/or damaged mattress when you move out.