Yes, two expensive projects that got nowhere. The flying boat was on its way out, but Saunders-Roe didn't seem to realise that. The Brabazon attempted to compete with the luxury transatlantic ships rather than take a good number of passengers. Some of the design and production experience of the Brabazon was used with the Britannia, so it wasn't entirely wasted, but this didn't happen with the Princess, as no more flying boats of any size were produced in Britain. Saunders-Roe did have ideas of the Queen, a five-deck flying boat, 300' long with a 300' wing-span, powered by 24 (!) Conway engines, but not surprisingly this stayed on the drawing board.
There were some contemporary US giant piston-engine planes that got nowhere in the civilian field. Douglas offered a civilian version of the C-74 Globemaster as the original DC-7; and Convair offered the Model 37 as a civil version of the C-99 (a transport plane that used the wings and tail of the B-36, only one produced so it didn't do well in the military field either), but neither was produced as airlines weren't interested. They were too big for the civil aviation market at the time. Also, the Boeing Stratocruiser, the civilian version of the C-97 (developed from the B-29) failed to sell in any great numbers.