Frightened by gigantic flies, Tash ? What flies are those, I wonder ? (he said, restraining the obvious and vulgar rejoinder which sprang to his lips - no, wait a minute, the plural of that is flys) We have a number of species. There are ordinary black houseflies, there are green and bluebottles, which are somewhat fatter, there are larger black blowflies, and there is a still larger black and white striped variety with red heads. None would be more than about two centimetres long though. Are these last ones the flies you saw perhaps ? I think if you live anywhere where there are animals, particularly cattle or horses, in the vicinity, you'll never be without flies even in the winter.