Vitsoe 606 Universal Shelving System by Dieter Rams
Designed by Dieter Rams back in 1960, it has been in production ever since. The system comprises of shelves, drawers, cabinets and rails that can be put together in which ever way suits your needs - and you can add to it as those needs change. Plus it can easily be taken apart and moved with you if you move house. The overall price will depend on what options you pick, but shelves start from £48 and cabinets from £495.
Visit the Vitsoe website to start planning your system.