I also wonder when these are going to be more broadly rolled out. The couple of specialist ISPs that offer them are incredibly expensive. Having said that, I don't really 'need' more than 300/50 but if it's available at a reasonable price .....

The expectation is that BT retail will sell the 550/75 and 1000/110 products from launch. Which means that whilst not necessarily cheap, there may be deals on (cashback etc).