Step 21 = Protect your mattress.
A mattress protector will prolong the life of your mattress and give you peace of mind . Make sure it is waterproof.
Pay for a decent quality protector so that it is actually fully waterproof, whilst not being sweaty and noisy to sleep on. Also make sure that it is deep enough to 'hug' the sides of your mattress firmly so it stays in place.
John Lewis do a range of good quality waterproof mattress protectors. Every bed in the house should have one.
In fact, children's beds probably need not one but two waterproof covers, for middle-of-the-night quick bedding changes. Hippychick make excellent cot-bed and toddler-bed (and larger) sized waterproof mattress covers. A great tip is to put two waterproof covers onto an 'at risk' bed at once, then you can whip the soaked top one off if the bed is made wet, and 'ta-da' you already have another protective layer there to get the bed safely through the rest of the night unscathed.
Waterproof mattress protectors can be easily washed at 40 C (with Napisan added of course), but they do take a while to dry. Another good reason to have a spare...