Fibre Speeds Mismatch

[#1]

I'm a bit confused so I would appreciate anybody's thoughts on this:
I checked on BT Wholesale's availability checker and was told I could get FTTC with speeds of between 50.6 and 30Mb - Range B.
So I signed up with Plusnet's service who also confirmed the speeds available.
Over a month ago the service went live and I get speeds of around 3Mb
So after a month of quite staggering Plusnet service I'm told that I'm too far away from the cabinet - 2.25Km
But what I don't understand is how the speed checker gets its so wrong in the first place, why Plusnet still reports my line speed/IP profile as 37Mb and why when I do a BT diagnostic test it says that acceptable range of speeds is between 20 and 3.42Mbps and that I should report this as a fault to my ISP.
What should I do?

[#2]

Well, at the very least it makes a mockery of BT statistics on bringing superfast broadband to rural areas.
As far as they are concerned they have given me and many houses around me, the ability to get 30+ Mb downloads - this is what their tests say. But the reality is, that they haven't. How inaccurate, I wonder, are the rest of their statistics and how much money are they getting from the government on the basis of these inaccurate figures?