That would be why they're rolling out ADSL2+, albeit slowly, with a trial running for the
last 4 months, 84 exchanges enabled in the beginning of May and the rest coming over the next few years.
On the other hand, I'd agree that BT Wholesale ADSL isn't the place to be if you want to download much but don't want to pay for it - the costs involved for the ISP quickly get crazy.
BT Wholesale aren't the only ADSL provider either - there's plenty of LLU options available that offer ADSL2+ and will let you download the internet for pennies a month.