Unfortunately that doesn't work for my line, I'm with talktalk so it's not a BT line. I'm certainly not as far as 4km from the exchange. I'll keep trying with the talktalk forum and see if they can discover why it is so slow for the distance we are from the exchange.
I have just checked on 2 friends numbers who live close by, one is 2.9km and one is 2.3. The 2.3 is closest to me, but the 2.9 lives closer to the exchange!
I have been looking on the thinkbroadband site and viewed the speed tests from my area. There haven't been many of them, but those recorded are similar to mine, the fastest being 4.5