BT Broadband - video streaming difficulties

I live in South-East London and use the BT Broadband upto 10Mbs and have had streaming difficulties since the beginning of this year. BT have recently fitted fibre to the local cabinet and keep trying to persuade me to upgrade but I am loathe to do so with my current experience. The basic problem is that BBC iPlayer/ ITV etc will only download/play intermittently. Usually running for a moment only and then buffering. BT argue that they don't support BBC/ITV and their speedtester shows sufficient speed. I have logged a query with iPlayer but they don't reply. Tbb's own video test does not download either. BTs [so-called] Desktop Help can find no difficulty. Is anybody else finding similar snags? All views will be welcomed. Regards

Perhaps there is a problem with your phone line? Could you post the stats reported by your router? See http://kitz.co.uk/adsl/frogstats.php