However even though (per the graph) it is (under thermostatic control) 'on' for only a couple or so of those seven hours per day, that still represents a substantial proportion of my total consumption - "a third" might have been a bit of an over-statement, but it is certainly usually more than a quarter.
Rather than having it come on at 1:45am to do the bulk of the heating, then cycling on and off several times to replace lost heat - why not if you can, have it start the bulk heating cycle at 6am?