You should explain to your new creditor that some of the amount they are pursuing has been reduced via the Courts. It is up to your new creditors to accept this reduction or not. However it would be plain daft to pursue you for an amount which is clearly now incorrect. If pursued your defence is simple: I don't owe what my creditor says I owe. Your creditor, if acting with any amount of sense, will realise this.
It will be up to your new creditor to seek any damages from your old creditor for their loss due to the imposition of (I presume) unfair charges.