I don't think that BT is the problem OP tbh, normal broadband is shit in most areas outside the cities in all of the UK regardless of ISP. (used to be with sky and had similar shitty speeds)
Its likely more to do with the quality and age of the phone lines going to our houses as well as the relative distance between you and the street and main exchanges.
If you are lucky enough to be in a infinity area then you get speeds like this, I struck lucky on a couple of accounts as my house is literally 200m away from the street exchange and less than a mile from the main BT exchange for the whole area.
[http://www.speedtest.net]