GUIButton not showing

I've haven't found any examples of how to use this component and haven't found and forum topics that cover, and of course there is little to no documentation.

I have a control derived from GUIBitmap. I want to place a GUIButton on it. here is my init code;

GUIButtonStyle exitButtonStyle = new GUIButtonStyle();
exitButtonStyle.Bitmap = @"data\images\ExitButtonActive";
exitButtonStyle.Focusable = true;
exitButtonStyle.FontType = "Arial22";
exitButtonStyle.IsOpaque = true;
exitButtonStyle.HasBorder = false;
exitButtonStyle.PreserveAspectRatio = true;
exitButtonStyle.AutoSkin = true;

this._exitActive = new GUIButton();
this._exitActive.Name = "exitButton";
this._exitActive.Style = exitButtonStyle;
this._exitActive.OnGUIGainFocus = this.OnExitFocus;
this._exitActive.OnSelectedDelegate = this.OnExitSelected;
this._exitActive.Position = new Vector2(150, 200);
this._exitActive.Size = new Vector2(100, 50);
this._exitActive.Visible = true;
this._exitActive.Folder = this;
this._exitActive.ButtonText = "Exit";
this._exitActive.Layer = 1;

Problem is, when I run it there is no button. I have another bitmap on the same control which displays fine. Cleary I am missing something here. Any insights?

Thanks