Ah, another Hesham 'mystery' that is not a mystery . Most of the answers can be found on Wikipedia.
During the war the majority of flying boats in Royal Navy service were developed at Felixstowe naval station by Lt John Porte, based on, and extrapolated from the Curtiss America twin-engine flying boat. As Felixstowe only had limited production facilities most were built under licence by a large number of boat yards and aircraft companies. One yard undertaking this work was Camper and Nicholson and they amalgamated with White, Allom and Company, another boat builder, to form Gosport Aircraft Company early in the war. In 1919 they acquired the services of Lt John Porte as chief designer and the designs you have posted are his work, several straight developments of his work at Felixstowe. Unfortunately he died the same year and the company was dissolved shortly after.
Incidentally, one of the flying boats proposed by Gosport Aircraft in 1919 was a ten-seat machine designed to carry men and equipment to the site of a forest fire, in Canada for example, or some other disaster site. Quite possibly the very first aircraft of this type put forward, the Gosport Fire Fighter is arguably the un-built ancestor of today's water bombers.
Canadian Vickers of Montréal may well have built the first aircraft specifically designed to help fight forest fires, the twin-engine Varuna flying boat.