What happens to a circuit breaker at overvoltage condition?
From the data sheet for your device the...
...rated impulse withstand voltage is 6 kV conforming to EN/IEC 60947-2
So, I doubt it'll have any problems with 250 volts.
But, as with any mains AC supply line, it can typically rise and fall by 10% quite often and, 10% of 240 volts is 24 volts hence, you can expect to see periods of time when the supply is as high as 264 volts AC AND, any breaker worth its salt will handle this slight over-voltage without batting an eyelid (if it had eyes).
You might have heard of 264 volts before; it's quite common for SMPs units to work across a so-called universal range of 85 volts to 264 volts. This is how the 264 volts is founded i.e. 10% higher that 240 volts.