Whats wrong with my economy 7 water heating?

Hi,

I have recently bought a flat and it has economy 7 water and also storage heaters. I have managed to test the storage heaters and they appear to work fine.

The problem I have is that when I moved in, the booster switch for the water was the only thing that was working, so for a week I had to turn on the booster switch for an hour before I went to bed in order to get enough hot water in the morning for a shower. I got an electrician in to look at the off peak switch and it appeared that the wiring was burnt out which caused the fuse switch to blow.

He managed to fix it and the off peak switch works and the light even comes on, however I have left it for two days and both mornings I have no hot water, its barely warm, I then have to put the booster on, doesn't this defeat the object of having economy 7.

Anyway, I'm not too sure whats wrong with the water heating now as I have checked the thermostat and it is turned the same way as the booster switch, does anyone have any ideas of what could be wrong with it?

Any help would be appreciated.

Thanks