Be wary of believing the download speed you've quoted. With only one exception (which definitely isn't the dire TalkTalk) all UK ISPs operate a system of 'traffic management' which prioritises some traffic above others. While their webpage only cites P2P services and newsgroups as the most likely types of traffic to be deliberately allocated slower speeds, it's well-known that TalkTalk is one of the ISPs which hates video-streaming services (and would, for example, like to see the BBC iPlayer service discontinued until there's a better broadband infrastructure available in this country):
http://www.talktalk.c...ic-management-policy/
Further, TalkTalk keeps prices low by offering an abysmal contention ratio of 50:1. That means that you're sharing your broadband connection with up to 49 other users. (Any decent ISP will offer a contention ratio of no worse than 20:1. My ISP, Claranet, has a 7:1 ratio). If you only pay a 'pound shop' price for your internet connection it's unsurprising when you don't get a 'Harrod's quality' service.
Chris