There's also a broadband speed checker on the BBC website, which has the advantage of telling you whether your speed is good enough for different iPlayer services:
http://www.bbc.co.uk/iplayer/diagnostics
Some programmes on iPlayer offer a lower bandwidth option (located at the bottom left of your screen), so it might be worth trying that. Otherwise you need to hassle BT to provide you with a decent service.
You can theoretically use iPlayer with a speed of around 2Mbps but I'd advise that closer to 5Mbps is really needed for a fully reliable service (without the 'buffering' that you've been experiencing). The speed you get is largely determined by how far away from the exchange your house is but 'contention ratios' can also play a major part as well. Your ISP's contention ratio determines how many people share the same connection at the exchange. With BT that's often 50 to 1, so there are 50 of you all trying to use the same connection, which means that you'll all get very slow speeds at peak times (e.g. in the early evening). Better ISPs use a contention ratio of around 20 to 1, with ISPs mainly serving businesses (such as Claranet, which I use) offering around 8 to 1.
The
type of ADSL broadband connection you get also affects your speed. The standard service offered by BT Wholesale to other firms (and to BT Broadband) is 'ADSL Max'. However if you ask a decent ISP to change it, you can get 'ADSL2+',which effectively doubles the available speed. I'm not sure though, that 'ADSL2+' is actually available to users of BT Broadband because their Home Hubs reserve half of the available bandwidth at your location for other users (i.e. people out in the street who use your router to access BT's Mobile Broadband service)
So it's not good old Aunty Beeb that's 'c*r*a*p' [as suggested in your post] but BT!