I think you are right but I don't have a separate tlb file for any other
components. I searched the registry and removed all references to my COM
Object, ran the object from its exe and that set up the registy entries on
its own. That then allowed me to add the reference.

What I did find was an entry in the registry for an item that wasn't
showing up anywhere else in the interop dll.

I was then able to invoke as follows:

Type m_nest = Type.GetTypeFromProgID ("NestOle.Document");
                               
            object ibaseObject = Activator.CreateInstance(m_nest);

            object[] arguments = new object [] {"c:\\nestmgr\\batch\\13.bat"};

            m_nest.InvokeMember ("goNest",BindingFlags.Default |
BindingFlags.InvokeMethod,null,ibaseObject,arguments);

This works, but is not quite as tidy as other COM componenets that just
needed adding as a reference, instantiating with "new" and calling their
methods. I can obviously now write my own wrapper class based on this to
simplify the method calls.

Does this mean the COM/tlb are not written "correctly" and so VS is missing
this component when creating the interop dll or have I missed something.

Thankyou for your help Peter