My experience with Octopus, for a Daikin 8kw: Broadly speaking they were fine, but some schoolboy errors made when rushing to finish.
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Tank thermometer wasn’t installed correctly (and wasn’t even connected!), and so the tank was overhearing and the D2 pump (which is bloody noisy!) was firing at 2am to release the pressure. Woke up the street, pretty much.
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Unit settings - they just default to what Octopus tell them, but might not be right for your house. It is trial and error (see Tuning performance of Dakin 8kw Altherma 3 - #15 by divenal) but the main thing for me was the CH pump speed was set to low, which when you did the maths, meant insufficient heat output and so my house wasn’t getting warm. Now that’s been set to high, it is fine.
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In relation to the above, I am playing with the weather curve and modulation settings, and TRV settings, to get my house right. At the moment (the last few days have been cold) my heating is kicking in 4 times a day. My COP is about 3 which is poor - it should be more like 3.5.
An FYI that you might find it is no cheaper than gas - it really depends on your house. I’ve got 13 kWh storage which really helps, but today (3c outside) the battery is basically empty by midday, and everything else is peak rate - I’m paying £5/day electric at the moment for a 3 bed semi, 90% of that is heating.
Ed