Jen, I am so angry on your behalf. Why do people do things like that. It is so unfair on the person who misses out. In our case, we were selling and got to the point of discussing exchange when the buyer changed his mind. That cost us £700 in legal fees.
The trouble with changing the way it is done, is that people are angry when it happens to them but because we each buy and/or sell so rarely, that anger subsides and is forgotten about.
I have actually written to a government minister about the ridiculous way property is bought and sold in England but the reply was laughable. I was told I could ask for a non returnable deposit on acceptance of the offer!!! As if anyone is going to pay that.
I hope you find something soon and that the vendor doesn't let you down again.