I did a car park once in Cwmbran once. It was one of these covered ones and we did not have one single job. If i had a leaflet under my windscreen wipers i wouldn't mind because i know what it's like being self employed.
The proble with this is that you do not know what area and type of house they come from.
At least by posting to houses, you get to pick the good areas where you think the work will be forthcoming, and in an area local to you. I priced a job once without asking the area. Because the dialing code was a local one to me, i assumed it was near, but infact turned out to be further out.
Suffice to say knowing your luck, your responses will be from areas far away.
Dave