I found the solution which is to do with SelectionStart as stated above but it has to be done after the TextEdit is completely loaded.
protected override void OnShown(EventArgs e)
{
base.OnShown(e);
textEdit1.Text = @"C:\Users\xxx.xxx\Documents\xxx\CODE\test\inner test\another\another\filename.xxx";
textEdit1.SelectionStart = textEdit1.Text.Length;
}
All thanks to Devexpress.