OK, I've tried the first option, probably done something majorly wrong here though - I just get an empty dropdown box - there is definitely an Assessor in the table.
Here is the properties section for the combo box (to show you I put it in Row Source... whether that's right or not I don't know.)
And below is the query I used to build it.
I assume I won't need the Search button for this method?
Also I haven't done anything to the Assessor Details in the form to get them to populate yet, how do I go about that?