Wash the lettuce, tomatoes, grapes and rocket. Cut the lettuce and rocket into bite-sized pieces. Cut the onion into small cubes, quarter the tomatoes and halve the grapes. Crumble the feta and mix everything in a large bowl. Shake the honey, vinegar, salt and pepper well in a well-closable container until the honey has dissolved, then add the oil and shake well again until everything is well mixed. Arrange the salad on plates and spread the dressing on top.