Problem solved. Different electrician checked the consumer unit and put the wires back as they should have been, and now the socket circuits are not joined. Unbelievable my first electricians was suggesting the property probably needs a rewire when the issue was, as many on the forum suggested, wiring on the consumer unit. Thanks everyone for your help.
Thank you all, for your help. I'm glad I came here for advice. I've left a message for the company owner (who gave me the report) so that he is aware the problem is solved by sorting the consumer unit - I'm sure he can figure out his electrician didn't do the job properly. I'll just not use them again, and won't recommend them.