I can easily say what's been the worst thing during our vacation - the wasps!
There has been so many of them, everywhere we have been. Extra yucky during those hot weeks when they got so lazy from the heat, and just sat in the grass for example - you had to be really careful and watch your step.
We are lucky we haven't been stung (*knock on wood*), still they have been extremely annoying when we have tried to sit outside and enjoy our meals etc.
Such a pain.
(Picture borrowed from www.chelmsford.gov.uk)