Right, so not the same. As it has been explained to me heizungsstrom allows people in Germany to create hot water buffers at a strongly reduced price per kWh during the night. Thus the hot water is already there for comfort when the heat is turned on in the morning. Your setup seems very tricky to me as you are essentially deprived of any heating during a number of 40 minute periods spread throughout the day and the only hot water you do have stored for comfort is in the radiators themselves.

I suppose if your pattern for turning on/up the heat stays clear of those 40 minute "blackouts" that will work just fine with Evohome. If I were in your place I'd probably use a timer as a secondary trigger for the boiler, say 5 minutes before a planned blackout period starts in which I may be likely to generate a heat demand. You might need a bigger and/or better insulated boiler for that though.

PS I think the Evohome phone app has the same .5 degree resolution as the central console. You should have a look a the various home automation projects, e.g. Domoticz supports Evohome with a temperature resolution of up to two decimals. If you are into programming you can also create an app yourself. Libraries for accessing the API are available in various scripting and programming languages, like python, js, cpp and c#.