Hiya Dave,
Try this:
Enter the coordinates in the googleMaps as you have already done. (54.83164419215485 -4.216175079345703)
Open file googleJavascript/wagmp_map_x.php (x = whatever number your map is)
Find the line (somewhere around line 150-152):
infowindowtext: '<span style="font: 12px Verdana, Arial, Helvetica, sans-serif; color: black;"><?php echo str_replace("'", "\'", "<strong>Coordinates:</strong><br />(54.83164419215485, -4.216175079345703)"); ?></span>',
Change it to:
infowindowtext: '<span style="font: 12px Verdana, Arial, Helvetica, sans-serif; color: black;">Address line 1<br />Address Line 2<br />Address Line Etc<br />Your Postcode</span>',
That should locate using the coordinates, but show the address you want it display.
Looks like this