I've got one. It uses part of the under stairs space so bottom end has very sloping ceiling. Top end has window with boiler above and a concrete marble shelf under which I store my wicker picnic hamper <well posh>
It's about 2 m x 7 m and I put up really strong shelving with London brackets to take the weight of all the grub which is all stored in there.
I like getting bits and pieces for my pantry. I got an iron holder a while back. And I've got a special shelf for spices. And I'm thinking of putting a brass coloured rail in for hanging dried herbs.