Both Okra and Amaranth like warm to hot temperatures, and full sun. Both are tall plants, and okra ia a heavy feeder. Amaranth can survive with less fertilizer, but will give better yields of edible leaves or seed if it is fed consistently. Unless you have an exceptionally hot, sunny spot to put them in, I would expect them to do better in a greenhouse in the UK. I was unable to find a days to harvest for 'Haritha', but most okras would be better started early indoors with very bright light, or in a heated greenhouse.