Looking at the traceroute working and one failing I'd guesstimate there was an issue between these two hops:
5 22 ms 32 ms 13 ms win-bb-b-so-700-0.inet.ntl.com [62.253.185.142]
6 16 ms 15 ms 32 ms bre-bb-a-so-100-0.inet.ntl.com [62.253.185.197]
Once that issue was resolved all was sweetness and light again. Probably dirty fibre, dodgy transmission card or something equally dull