HeatAndPlumb.com and ScrewFix offer a wide selection of hot water cylinders on their websites. Both retailers carry vented and unvented cylinders. Both companies are located in the United Kingdom and may charge extra fees for shipping and handling outside of specific geographic areas or for expedited shipping.
HeatAndPlumb.com currently carries 14 different types of hot water cylinders, as of 2015. It also offers several different kinds of accessories and tools for these cylinders, including programmers, trays, flanges, and trays. ScrewFix.com currently offers 66 different models of hot water cylinder on its site, as well as immersion heaters, immersion timers and expansion vessels.