I'm sure someone else will know more about this than me. But historically, UK was 240v / 50Hz whereas most (if not all) mainland Europe was 220v / 50Hz (contrast this with US at 110v / 60Hz).
I seem to recollect that it was mooted that 230v / 50Hz was to be the new standard (for Europe?) and that the Uk would be stpping down. All appliances would still work as the stated nominal voltage is just that a nominal value that is targeted. In practice the voltage fluctuates all the time due to a variety of factors affecting the grid and appliances have quite a wide tolerance.
Accordingly, I see no reason why a UK PSU shouldn't work in Hungary.
You might find the following interesting reading: