I think the guys you are referring to have already made it clear that their minimum charge is thirty pounds.
I have successfully cleaned carpets today, which were supposedly cleaned over a week ago, but were still wet, in patches and covered in dark patches and what looked like streaks of sulphation on stair risers.
Before taking the job on, I cleaned a small room a couple of days ago to reassure myself that the carpet would clean.
I was unable to carry out this job when phoned, as I was in Spain and someone was found in the local Paper.
Apparently the 'cleaner' arrived in a car and had a hire machine, but clearly new nothing about c/c he was contacted by the client but refused to return and the newspaper referred to their disclaimer.
Anyway, the job was done successfully with the Ninja at max' heat and working two floors up - at around 75 feet from the machine - the person who made this mess was no carpet cleaner, but simply a chancer who made someones life very miserable and could have cost them a couple of thousand pounds, had she not been refered to me.
I have seen a similar job taday where a long established c/c business, has left a customers 80/20, in a patchy state, which I'm expexting the Texatherm system to resolve.