Eggcellent, page-74

Note 20 2016 Annual report shows a reconcialiation of Npat to cash flows for the year. Comparing these notes from previous years will answere your questions as how these cash flows have been increasing.
And yes it has been less costs.
Sustainability of cashflows is different from sustainability of rate of increase of cash flows. I am pretty sure that cashflows are sustainable assuming that sales remain the same.

Well if we can reduce the working capital by 2 million and give the same return this points to increase effeciency in the business not to any window dressing.