Thank you for the question. This is not a breach of GDPR. There would only be a brach if you have supplied personal data to a third party without the person's consent which has not happened. The best way forward would be to cease any communication and remove any photo which you do not own. I don't see that they would have much basis for a legal action against you.
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;
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