Hi Hayley,
Tricky. There will be conflicting answers to your questions. But this was our experience.
We used an independant agent who recommended a solictor and after meeting him we felt comfortable with him so instructed him to deal with the transaction for us. (That was before I joined EOS and so didn't know that there were people that had experienced problems).
Anyway, I have to say he was absolutely marvellous and nothing was too much trouble, he acted for US and was very professional at all times.
The answer to your other question, we paid nothing for his services until we completed.
As I say, that was our own personal experience but there will be other advice for you I'm sure.