You've definitely touched a nerve with me, so I'll go ahead and answer you as best I can.
retirement homes under the sun
This is my dream. And London is one of my favorite cities, so having a retirement home under the sun in say, Kensington or Knightsbridge would be ideal.
Oh, I know that some think London is less than "sunny" much of the time, but on the odd occasions when old Sol shows himself it can be quite nice, actually.
How do you plan to market these homes? Would it be possible to pay in various currencies? I think you would do best to restrict your offerings to the higher price ranges, so people could set up 50-year mortgages at the current low interest rates.
I would like to know some fears to have prevented you from purchasing overseas
Good approach. I have a great many fears in this regard. One of them is a fear of crossing large bodies of water. Perhaps you could arrange some sort of alternative travel scheme for buyers like me. How do you see me getting from the American Midwest to London in order to take possession of my retirement home under the sun?
Another of my fears is being taken for a sucker. Once I managed to go on an inspection tour, I found that the "high, dry Florida savannah property" I purchased through a magazine advertisement was actually snake-infested malarial swampland, I began to get a bit skeptical of those who market such opportunities. Of course, I don't suspect you of any nefarious intent, but I wonder if you might provide some references to your good character?