I am sorry to hear about this matter, the difficulty is that you have entered into a legally binding contract with them. If you default on this, then you are in breach of contact allowing them to terminate it. Therefore if they are not willing to accept repayment and come to an agreement with you they have the right to have the car returned to them. If this is what they are asking I would advise doing it, if they take you to court to enforce this, you may also be liable for their legal fees in addition to the arrears. If you feel you have a defence to this, you could potently defend the matter, however form what you have provided it sounds as though you are in breach of the agreement.
I shall provide you with a helpful link that will assist you in finding a solicitor/representative near your local area. This will provide you with someone nearby your area who can assist you if required.
I hope this information proved helpful. You will find a local solicitor who deals with these matters on the law society webpage which is as follows;
https://www.lawsoc-ni.org/solicitors (N. Ireland)
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