Others have made the point also, but be aware that your loft space will likely be subject to seasonal extremes of temperature, from very hot to near freezing, which can have a damaging effect on stock stored and used there. Both plastic and metal will expand and contract with, sometimes, very expensive consequences. However, loft space can be used successfully, but ideally it should be insulated and boarded-out first by a reputable builder with loft space conversion experience. They will also move or adjust the loft hatch if required and can install a retractable ladder for better (and safer) access. Building Regulation approval may be necessary from your local authority. It will cost a bit, but you'll need to do it only once and well worth it.