It is possible that the BTO engineer put you on a better port at the exchange temporarily.

Also the new DLM software is bumping up the connection speed of many people.

When on the ADSL package I was on WLR3. The maximum speed this allowed was 20mb for a long time. I knew that the connection was capable of more from some private discussions. Had I been on the full Sky DSLAM I could have expected better all along. The new DLM did improve things a little at one point but not a huge amount.