allways have to press the boost to get hot water and the boost button only works during the day???

this is my first experience with hot water electrics and boilers and wall heaters... ive read alot of these problems on these sites and wondered if anyone can help.. especially mike the boilerman he seems to be pretty clued up on this stuff.. the problem is i dont have hot water. i have luke warm water to wash dishes clean hands etc.. if i want a shower i turn on the boost button wait half hour then i have hot water for a shower after that theres no more hot water.. this boost button only works in the day?? should i reset the timer on the left of the fuses?? should i switch the big green power button off then on again?? is this all linked to my wall heaters or are the water and storage heaters on the wall seperate?? sorry if i sound stupid, but i have no clue on any of this? id just like hot water when i need it. Thanks for your time..