I wasn't aware that Fletcher wrote three books for Liberator. I've only seen two but one does indicate a third! The Parkfield Miniatures website still lists one of them but the other is showing "out of stock". I can also attest to the quality of the "Spanish Ospreys" I was in Marbella last week and saw their book on the Spanish forces in Texas and it was beautifully produced, with colour plates as good if not better than anything Osprey currently churns out. In hindsight I should have bought it and relied on Google Translate to do some heavy lifting.
Good luck with your search.