Complex sentence: The British Royal Naval Air Service operated 35 of which ten came from Breguet, and 25 were built in the United Kingdom by Grahame-White as the G.W.19.
Split into simpler sentences: The British Royal Naval Air Service operated 35 of these aircraft. Ten were purchased from Breguet, and 25 were built in the United Kingdom by Grahame-White as the G.W.19.