I have been issued with court proceedings to recover money that a solicitor claims that I still owe them?

The solicitor did not realise that the money was outstanding for nearly 2 years. I was incorrectly advised by the law society that I did not have to pay it , and they have admitted that they got it wrong. My question is do you think that I should defend myself as I have tried to pay a major part of the money after explaing that I was incorrectly advised which I can prove in court. The proceeding is for a total of 2.2k which includes solicitor costs of 80 pounds. In a new letter today they have stated that if their claim is successful they will seek an order to pay the firms cost which they state is one thousand pounds. How can they do that if they are already claiming the 2.2k which includes costs. Are they trying to scare me into paying the full 2.2K