The normal scenario he found was: (l) look in window; (2) go inside, have particulars noted and get put on mailing list; (3) look at a few properties unescorted; (4) take it from there youself.
The main offenders were large chains with young, inexperienced staff. 'They seem to believe the potential customer is something of a chore, not someone to be cherished as the bread and butter of the operation,' Mr Henderson says.
The good news is that Mr Henderson found some highly commendable independent estate agents - so let's hear it for John Payne of Greenwich and Kinleigh of Putney.
Kinleigh ultimately sold Mr Henderson his home. 'It took about six weeks, several viewings, lots of phone calls,' he said. 'They were excellent: everything was done with the utmost politeness and a smile.'
When the large financial institutions moved into estate agency in the Eighties they were criticised for failing to appreciate the personal, local nature of the business. Some went to the wall, but those who remained claimed to have learnt their lesson. According to our readers, they haven't.
Nor have they in my my own experience. Last week I rang a branch of GA Property Services for information about a property. I explained I was the Independent's property writer.
It was clear the agent had not seen the property. Rather than pass me on to someone who had, he asked if I had a property to sell. No, I said, I was a journalist. I was passed on to the assistant manager.
I explained it all again. 'How much will it cost us?' she asked. I explained it was an editorial query and would cost nothing. But, judging from the letter I later received, referring to the owner's willingness to have the property 'advertised', this point was not grasped.