I have subscribed to GE Premium and written up my experience of the app:
https://homeenergyefficiency-reallife.co.uk/givenergy-scheduler-may-26-solar-13/
Good news for Wim/WW: I am sticking with WW. While the new app does have some new useful features I remain to be convinced about the "Smart Scheduler".
I have also signed up for Axle and this does seem to work (I have £12.99 just arrived in my bank account), so, yes, "WW integration with Axle Energy Grid Event would be a utopian combination", or at least pretty cool.