Virgin Media customers are in for a big treat today, because the UK-based ISP has just announced plans to double the average speed of its broadband service. Over the course of the next 18 months, top speeds will increase from 100 Mbps to 120Mbps, as part of a £110 million ($169 million) initiative. Users on 10Mbps, 20Mbps and 50Mbps plans, meanwhile, will see their speeds and bandwidth usage limits doubled, at no extra charge. The upgr