Since my last post things have progressed (a little). I am still studying for the PfCO so my evenings are busy and after a fair bit of testing I have now settled on a photogrammetry solution which is far more robust with GPS location data. It also allows export of .xyz cloud data which is easily transferrable to Archicad along with ready aligned meshes as long as the point cloud data has been defined adequately prior to export.
Once imported to Archicad as long as the parameters are correct in the setup of the project the point cloud inserts itself correctly to GPS co-ordinates.
Below are the 3D point cloud and two sections taken from Archicad.
Next stage is to do a drone flight over a completed project and align this with the design data as a test.