Mattress damage almost always comes from one of three things: folding, dragging across a dirty floor, or storing it on edge too long.
Don’t fold a mattress. The springs and internal foam aren’t built to bend, and most manufacturer warranties void if you do. Use a mattress bag (£8–15 from any DIY shop) to keep it clean and dry. Bin bags split halfway down a staircase.
Carry the mattress flat on its side with two people, gripping the seams rather than the cover material. In the van, lay it flat on a clean blanket if there’s space; rest it against the wall if not. Never stack heavy boxes on top.
King-size and larger? A man and van gives you the second pair of hands plus the van space to keep it flat.