What is the exact size of the HEMS unit in litres, to allow estimate where best fitted?

The Hems unit is not measured in litres per se; however to give you an example: an E Cylinder weighs 28 kgs and it is 1200mm long with 220mm width. The actual unit size including all parts and plumbing connected would mean an actual space of 400w x 1400L x 360h all in millimetres. G Cylinder is slightly bigger weighing 48 Kgs, and system dimensions are 400w, 1800L and 360H – again measurement are in millimetres.