After spending 2 days trying to get the GMAP Mod to function I have finally succeeded.
The solution is based on a post by iniebla in 2008 and I replicated it here for completeness and confirm it works.
It will hopefully save someone else 2days of work.
CHANGES THAT NEED TO BE MADE:
. on file /templates/wiki-plugins/wikiplugin-gmap.tpl change $feature_gmap, $gmap_key, $gmap_defaultx, $gmap_defaulty and $gmap_defaulty CHANGE TO $prefs.feature_gmap, $prefs.gmap_key, $prefs.gmap_defaultx, $prefs.gmap_defaulty, $prefs.gmap_defaulty (all occurrences; intended values are in array prefs in _tpl_var, not directly in _tpl_var as program supposed); if you have put gmap tag on a wiki page then you will see Google map on that wiki page.
. on file /gmap_wikipluging_save.php change $feature_gmap CHANGE TO $prefs'feature_gmap' (at beginning of file; similar reason that change in previous file): to have working 'Save current point' for new values for x and y on 'map and geotagging for this page +' option.
NOTE- WHERE 'feature_gmap' IS ENCLOSED IN '...' REPLACE THE ' WITH SQUARE BRACKETS. FOR SOME REASON THE EDITOR WONT LET ME USE THEM ON THIS POST.
All credits go to iniebla