I am pleased to say that I have recently been added to the list of independent researchers that is maintained by The National Archives. It took some doing: I submitted an application form and examples of my research work, and had a rigorous (but friendly) interview. Upshot is that my name has been added to the lists of specialist researchers who cover the following areas:
Foreign, Colonial and Dominions Office records
Registrar General of Shipping and Seamen and Mercantile Marine Records
Royal Air Force Genealogy, Biography and Operation Records
Royal Naval Operations Records
No bad thing.