This was reported in our local paper in Swindon,Wilts in Feb 07.
They were dressed in green t shirts with the name Bennett's Cleaning Company all over it,and were supposedly based in Bristol.
It was very believable and they were professional scammers,a lot of our neighbours fell for it.
My wife parted with 24 squid,and after discussing it I rang them to cancel,and was unable to contact them so just cancelled the cheque.
It's alright saying how can anyone fall for a scam like that but when people are offered "professional" services at a discount a lot of people will accept it as an honest offer,there are still a lot of trusting customers out there who take tradesmen at face value,if this was not the case we would all be out of business.
John.