Bit of bad news - most confidence tricksters are very personable people. If they weren`t, we wouldn`t be taken in by them and they wouldn`t be able to do their `jobs`.
As for the tarmac and PC work; in the first a written quote signed by the contractor(?) would have saved bother - always assuming you can get one!!!! And the second, it is not unreasonable for the `expert` to tell you exactly what he has done - again agreement that he will do this is best obtained in advance. Failing that an itemised bill???????