Madoka
Since you are using Madoka thermostat control, you might want to adjust the settings on the Madoka menu to get more accurate readings from it. I’ve seen quite a lot of self-heating from the blue LEDs and backlight.
Flow temperatures
I agree with Matt that you probably don’t want to go lower than mid-30s for the flow temperature. So I’d suggest you make your weather curve much shallower, 40C-35C perhaps.As Matt has noted on many occasions, the larger Daikin units (9-16kW) don’t have a huge range of operation for our normal sized houses, and we are running them towards their minimum output.
Monitoring
I don’t get any meaningful values from the MMI as my electricity usage shows up as basically 0 or 1kWh per day. (No one has seemed interested in looking into this, either Octopus or Daikin).
I’ve gone with ESPAltherma monitoring. Stephen has written a great post explaining how to do it here:
You need to be comfortable opening up the outdoor unit and probably want some experience with Home Assistant. It gives a lot of insight into how the unit is operating, but does rely on the accuracy of Daikin’s sensors. There’s debate on how accurate they are…
And of course, since you are on this forum, you could look at getting the full monty heat pump monitoring from
Continuous running or switching the unit off?
Again, a topic of some debate. While I think we all learn that running a heat pump continuously is most efficient, that requires the heat pump to be able to match all of the ranges of heat demand for your property. It’s likely that the Daikin 9kW can’t go low enough for medium sized UK houses, so continuous running is impractical on warmer days. On the cold days, you are probably better running nearly 24 hours a day, at a medium flow temperature (40C?) than asking the heat pump to ramp up the temperature in the morning with 50C flow - that will just defrost a lot.
Switching the heat pump off, either via thermostat or schedule, is certainly reasonable. It is very efficient not to run the heat pump 
I have been meaning to measure the ‘startup’ cost of the first hour or so until it reaches stable operation (after a previous heating cycle), but it depends a lot on ambient conditions.
I would suggest that if you are using thermostat control, have a look at the backlight settings mentioned above. I saw some horrible behaviour where the Madoka thermostat temp was reached, the blue light would go off and the measured temperature dropped and after a few minutes the heating came back on! Frequent on-off-on cycles for the heat pump are not good for efficiency, but if you are running it for a couple of hours at a time, it should be pretty good. (From looking at some of the 4-8kW units on heatpumpmonitor.org, it looks like they can be cycled a lot and still give decent efficiency! Grr.)
There’s a long thread covering some of these topics: