Sky has decided that it's time to get really aggressive when it comes to high definition in the UK, and to that end has slashed the price of its Sky+HD box to just £49. That's a third of the price it was early last year (£150) and is the satellite broadcaster's hope of getting many more subscribers hooked on pay-for-HD. In fact, thanks to a lot of enticing marketing and the lure of a variety of sports, films and other content in high definition, Sky has just had its best quarter -- in the three months to the end of December, 188,000 people signed up for high-def services, taking the total number of subscribers to nearly 800,000...