Worcester Bosch 24SiII Tripping off?

Some mornings the boiler has tripped the MCB in the fuse box. Then the board had to be replaced. It had tripped off a few times before the board went. It is still tripping off in the fuse box some mornings. It only seems to be in the mornings too after we have got up. The boiler is about 8yrs old and seems to work in all other senses. It is a rented flat and so any info that I could give to the landlord would be great as he didn't know what it could be and the repair man said that there is nothing wrong.
Cheers, Lee.