like the tees barrage shot, the blur of the water shows its taken with a slow shutter speed, i dont know why some shots are coming out grainy, if you post your exif data for the angel of the north we might be able to help, sometimes if the exposure isnt quite right and you adjust in photoshop its possible that you lift the grain from the shadows as you bring the exposure up, another possibility is you maybe using a high iso (or auto iso), for long exposures you want lowest iso your camera has,
heres a composition type of picture, your eyes read a photograph like a page, they start from left to right (maybe not chinese people lol), the idea is once you get to the wing your drawn down towards the centre of attention, lastly anything that is perceived to be moving needs space to move into , if this was a tight crop your eye would leave the page as it automatically follows the flight of the gull., cheers martyn