Cannot get TGMHeatmap to work

Question

We can't see how TGMHeatmap works, even using MegaDemo and heapmap.csv. The properties we set for TGMHeatmap are the same as for MageDemo (except language), we do this in FormCreate:

procedure TForm1.FormCreate(Sender: TObject);
begin
  DefLat := 52.189746;
  DefLng := -2.215933;
  GMMap1.RequiredProp.Center.Lat := DefLat;
  GMMap1.RequiredProp.Center.Lng := DefLng;
  GMMap1.Active := True;
  GMHeatmap.LoadFromCSV(0, 1, 'C:\Temp\svhscusts.csv', ',', True, True);
end;

and this in a button for displaying the Heatmap

procedure TForm1.BHeatmapClick(Sender: TObject);
begin
  GMMap1.SetCenter(52.189746, -2.215933);
  GMMap1.RequiredProp.Zoom := 13;
  GMHeatmap.Show := not GMHeatmap.Show;
end;

The format of the data file is (each on one line)

52.00240,-2.11490 52.00240,-2.11490 52.00200,-2.11400 52.00200,-2.11400 52.00400,-2.10950 52.00400,-2.10950 52.00400,-2.10950

Since MegaDemo does not [appear to] work as expected, perhaps using/updating MegaDemo would be the easiest way of explaining what isn't working (or what we are not doing correctly).

Excellent software, incidentally. If Google would reduce it's licence fees for small customers, we could use it properly