@Wayne-TP If it was reaching the set temperature when the schedule begins I wouldn't have asked the question!
 

I've attached an example of a radiator I want to reach 19 degrees by 7am. It "early starts" about 6:30am (having been in a period with no rules since 5:30am) but has only reached 15.8 at 7am. 
 

The cause of it having erratic temperature after about 8am is down to my wife opening a window to let out steam so ignore that. 
 

I'd have expected the valve to early start a lot earlier given how slowly that badly insulated room heats but it seems resolute on a 30 to 45 minute early start. 
 

it isn't only one, they all do that. 
 

As I asked in my post is there a maximum early start period or do I just have to wait longer for the valve to learn?

  @Wayne-TP the boiler flow temperature isn't the issue. My issue isn't how long it takes to heat up. 
 

The issue is that the KE100 is sold with early start, the promise being that the room will reach temperature at the set time. 
 

My house is poorly insulated and takes a good two hours to heat up. After two weeks the thermostats are still only starting 30 minutes ahead. So, despite the claim they learn about your house they demonstrably aren't. If they were then they would be starting 2 hours early, or at least when the previous rule ended, but they aren't. They are at best 45 mins early or 30 mins, hard to tell from the graph. 
 

Hence my question. Is there a limit on how early they will start? I've ended the previous rule with a 2 hour gap but the thermostat still hasn't figured out it needs to use that gap. Is it faulty by design or have I got 11 faulty by manufacture? Or am I somehow setting it wrong (although I don't see how)

Previously i used a Nest thermostat for the system and it happily figured out that it took 2 hours to heat a room and turned on accordingly, the KE100 doesn't seem to be as smart.