LONDON (Reuters) - British online supermarket and technology group Ocado reported ballooning annual pretax losses and a 27% fall in core earnings, mainly due to a fire which destroyed a hi-tech flagship warehouse in Andover, southern England.Ocado , whose shares have risen 35% over the last year due to overseas technology deals, said on Tuesday its loss before tax widened to 214.5 million pounds in the year to Dec. 1 2019 versus 44.4 million pounds in 2017-18.The loss reflected exceptional..