1. I agree - unless the property was not registered, £600 is a gross overcharge & a complaint should be made about this.
2. The solicitor who went out of practice seems to have been irresponsible. If he/she is alive & can be traced then it might be possible to get some recompense from him. The best way to proceed is to give the details to the Law Society & ask them whether they have any record that can be used to trace the solicitor; also ask them who should be made to pay for the reconstitution of the deeds.