When my MiL was moving, right from the start we told the owner of the flat she was buying she had a deadline six weeks ahead, which he said he was happy to meet as the flat was unoccupied. Except, of course, he actually had no intention of doing any such thing. Our solicitor, a close friend, kept chasing him but got no reply.
Finally, after the deadline had passed, we found a better flat, put an offer in and negotiations for that went ahead promptly. Meanwhile the owner of the first flat had still done nothing, we were not even anywhere near exchange. So we left it.
A month past the deadline he came back ready, at last, to start proceeding with his sale and we had great pleasure in telling him we were no longer interested in his flat as MiL was only days from completing on another property.