If you have a judgement against you in the courts this will remain on your credit rating for 6 years. If you pay off the money owed you can request that the creditor sends a note marked "paid in full" to the credit rating companies and any future enquirers as to your credit-worthiness will be informed of this, and often take a more lenient view, though the debt will still remain on record.
Check with your bank or local CAB for a booklet from Experian, one of the largest credit rating companies in the UK, which will explain this procedure in full.