LONDON (Reuters) – Britain and the United States have agreed to collaborate on future commercial spaceflight missions, boosting opportunities for firms from both countries to operate from spaceports in either, the British government said on Friday. Britain said the partnership, signed by transport minister Grant Shapps and his U.S. counterpart Pete Buttigieg in Washington this week, would make spaceflight easier and cheaper. The new declaration “lays the foundation for rockets, high-altitude balloons and spaceplanes to lift off from spaceports across the UK very soon,” the British government s…