I use one from B&Q for storing everything lees the tent, chairs and tables. I can fit large box of kitchen equipment, water can, kettle, cooker and stand, EHU and various bits and bobs. Link
Oh thanks for the link pds400 - I was considering something a bit bigger tho - the Keter store-it-out perhaps - link
The tent is currently in the shed - in its bag - never had a problem with it stored there but I did wonder about condensation in plastic or metal boxes. Maybe it is worth me keeping the tent in the shed then and put the other stuff in the box.