With the Eco7 thing, first find out what time yours flips and remember that is the GMT time so when on BST remember to alter any timers. The storage heaters run through a different circuit, not sure if it self adjusts.. I remember taking ours storage out and a new board put in, moving to a combi boiler...
Anyway just something to check. You Electricity board should be able to tell you (not the same as your supplier) They should also be able to tell you which of the numbers if night and day. Some can be different
We have a new small white digital box. 1 is night, 2 is day and 3 is combined.
Our old rotary had to individual dials.
check what your DD is set to, they'll tell you if they are changing it. But yes, it's to even out over the year.