I did it!!
I added this to the blynk.js in the blynk-library
this.WidgetMAP = function(vPin) {
this.pin = vPin;
this.location = function(index, lat, lon, value) {
var info = [index, lat, lon, value]
self.virtualWrite(this.pin, info);
}
};
And can now use this to post to the MAP component:
var mymap = new blynk.WidgetMAP(16);
mymap.location(51, lat, lon, "GPS");
So issue solved!
I’m going to try to add a pull request to the js library