Hi queenlex,
I am not entirely sure how you figure buying to let works out for you? Am guessing that what you are trying to do is get a buy-to-let mortgage and use the rent paid (i.e. in this case your rent allowance?) as the income which pays the mortgage? I suspect that might be a little <ahem> "innovative" for either the tax man or for social welfare. Essentially your rent allowance is not paying for rent in that case it is paying for whatever property you would acquire.
Irrespective of whether or not it is a runner, I don't think you are going to be in a position to get even a small mortgage, you don't indicate that you have any savings and your current income is from a combination of a limited pension and the state. I think the other posters are correct, get your name on the housing list and in the interim, keep trying to find a place to rent. There will be somewhere out there willing to rent to you.