That sounds about right - the A in ADSL is for Asymmetric, i.e. uploads are usually slower.
What is it you are trying to achieve here - what do you need the faster upload speed for, exactly?
As there may be another solution,
What package are you on?
Slower uploads are normal on UK domestic connections and have been since "broadband" launched as an upgrade from dial up
When i was on ADSL my download speed was 24 and upload about 6
now on VDSL (FTTC) my speeds are 58 down and about 12-14 up.
Even if you sign up to BT FTTP on the top expensive tier with 900 down the upload is signifficantly lower at 100mb