Just to concur with what people have already said. Unless there is cable available in your area, BT will supply the line to your house. So check with BT if "fibre to the cabinet" is available in your immediate area.
BT have a program of putting fibre optic to the cabinet, which will be "down the road" from your house, if you live in a urban area. So if you see a brand new green cabinet on your streets, normally close to the old cabinet, you should be able to upgrade to BT Infinity.
Check with BT if this service is available. If it is, go for it, as its your only hope of getting a much better speed. I made the change in February this year and now get 37 mega pixies, and like FrogNog, I too am very pleased.