I (regrettably) let a friend between places stay on my sofa bed for a few weeks whilst between places. They have covered my living room carpet in mud, spilled drinks and cigarette ash. Carpet is a complete state. If I owned the place I'd be tempted to replace it, but it's rented. Is there any kind of carpet cleaning kit I can buy from the supermarket/DIY places that would do the trick, or should I look at buying a steam cleaner or even hiring a more heavy duty one? Help!