The cleaning machines really do work!!!! And it's not actually that hard - I think we got one from Travis Perkins - it was actually quite fun (and this is coming from someone who usually subscribes to the theory that there is no point in doing housework - six months later you have to start all over again! It brought the carpets up a treat, and was really inexpensive compared to "professional" cleaners.
I will suggest you just go with a reputed company which is using latest technique for carpet cleaning like dry cleaning and steam cleaning. it's lucrative for those person they want quick and reliable service