Don't know much about the background of this, but if the CCJ is paid in full within 30 days of being lodged, it is not noted by credit rererence agencies.
After this time, it stays on for six years (even when it is paid - just shows as being satisfied). If you pay the court directly, they automatically inform Registry Trust (they tell the credit reference agencies). If you pay the creditor, you will need to provide the isuing County Court with evidence of the payment in order that they can inform Registry Trust.
You may have to contact registry Trust yourself if the courts are taking a long time to contact them - they will require a certificate of payment which you will get from the court.
Hope this answers yours question.
Steve