I should have looked harder. ?sometimes you just have to look again I suppose. I have explored the SetUp button and options at length, and have found in there a section called "main menu". Looking through there I found the "Go To" button option, which was not installed. So now that I have installed it as part of the profile menu for my activity, there is a Coordinates option in that sub menu, allowing coordinate navigation.
One question though: in putting in UTM Coordinates on the 450 there is seven spaces for seven numbers on the Northing and Eastings in the 450 coordinates "go to" menu. If I am short the last digit on a coordinate -- so six numbers on the Easting and Seven on the Northing, will that make any significant difference on the ground?
Example of a known coordinate from a book I would use is: Zone 55 731450E 6370300N Notice six digits in the Easting and Seven in the Northing.
(In case you want to look at it, it really is El Dorado in Australia!)
Thanks for the replies, they have been helpful to me an I appreciate your responses.