steppemum I need to defend my short letter here!
It doesn't matter if people skim read it or not. Once they see the point (only three very short paragraphs) it will either be of interest to them in which case they'll then reread focussing on the few details, or more likely it won't be of interest to them and they'll bin it.
The OP needs to present herself in the best possibly light if she's going to make the effort of doing this in the first place.
If the targeted houses are thinking of selling a polite, precise, articulate note would be of interest. They may be more keen on thinking of liaiasing with someone who presents themselves well than someone who sticks a grubby badly worded note though the door. I know I would. If they aren't thinking of selling, it doesn't matter what they think of the note anyway.
I think Crystals idea of a subsequent follow up letter/note/leaflet is a good one, at some stage, if nothing is gained from the first letter drop.
The chances are it won't work. But as the op is only looking in a small area, I think the fact it might work is worth it, for what is a minimal amount of effort should it produce your dream house.
Some vendors wouldn't dream of selling in this way anyway, they like the security of using an Estate Agent.
Crystal - good luck. Why didn't you buy one of the three houses that subsequently came up for sale?