Consumption of 5 wash hand basins and size of direct unvented cylinder

[tapdancer]

I've 5 wash hand basins (2 x gents toilet, 2 x female toilets, 1 x disabled toilet). I'm planning on supplying the mixers from a direct unvented cylinder. The furthest point is the disabled wc is about 7m from the cylinder location. How do I work out what size of cylinder to use? What is the consumption of the basins likely to be?

 

[kirkgas]

It's covered in BS6700 that we use for an exercise for the plumbing apprentices, it gets them to work out delivery rates and pipe sizes, I will try to look for it over the weekend