Hello and thanks for using Just Answer.
My name is ***** ***** am happy to assist you with your enquiry.
From the legal point of view, we Solicitors HAVE to speak to our clients before we exchange Contracts, to get authority from the client to exchange Contracts, and to get their consent to the proposed completion date.
Unless you had therefore authorised your Lawyer to exchange Contracts and complete "as and when the Seller wanted to" during your meeting, your Lawyer has been negligent as he should never have gone ahead and exchanged without checking with you first.
I note you had told him that completion needed to be by 5th July, so there does not appear to have been any good reason why your Lawyer exchanged and agreed the completion date without speaking to you first.
As regards ***** ***** can do, legally, completion is set for 10th August, and you won't be able to change this. You will therefore have to contact your Lawyer this morning, explain their negligence, and tell him in no uncertain terms that his Firm will have to be responsible for any additional costs incurred by you due to the fact you will have nowhere to live after 18th July.
I hope this assists and sets out the legal position.