Found where I'd gone wrong. Where you create a custome page/control the code behind file has to be edited.

In the codebehind file for the ascx file I had to change the class to inheret from PortalModuleBase and override OnInit and add InitializeComponent()

public partial class UnitDetail : PortalModuleBase
{
override protected void OnInit(EventArgs e)
{
InitializeComponent();
base.OnInit(e);
}
private void InitializeComponent()
{
this.Load += new System.EventHandler(this.Page_Load);
}

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