By Li-mei Hoang LONDON – Fueled by the boom in online sales for the latest trends, London’s designers are finding new ways to deliver instant gratification to fashion hungry shoppers, amid high hopes of boosting growth in the sector. British retailer Topshop, whose website attracts an average of 4.5 million hits a week, launched a new digital “first” on Sunday by letting shoppers buy six ready-made items from its latest collection immediately after its show at London Fashion Week. “As we know, everyone spends all their waking moments on all these new platforms, gadgets, Instagram and Twitter,” said Philip Green, the owner of Topshop brand and retail conglomerate Arcadia.