To get it working you also need a twin and earth cable from the ASHP immersion heater output to go into the e-sense port on the Eddi.
If you have 2 x 2 core cables you “could” use one for the smart grid relay and one for the immersion port as you will not be pulling any current through it and you only need a live and neutral for the e-sense. The actual power is pulled from the Eddie’s main power input.
That would allow it to work with full smart grid and immersion from the madoka.