How much is National Grid really buying from the Demand Side?

At the Power Responsive conference on Tuesday 26th June 2018, National Grid suggested that they had already met their June 2015 target of procuring 50% of balancing services from demand response providers by 2020, as 50% of STOR was now being provided by non-Balancing Mechanism (NBM) participants. This was also reported in the Energyst today: