thank goodness you didn’t reply with “jambo” - my pet hate!!
I’m not sure that you would get Forum support for actually placing your sit in York. There’s a lot of negative feeling about inaccuracy in HO listings.
However, adding “York” prominently (in the first few words of your title, because the full title doesn’t always display fully on listings 
) should get the results you seek.
Kibera is certainly challenging. We had a housekeeper who lived there & we helped his family to be able to stay away in his home village where they were much safer. That was 20 years ago but I’m sure nothing has changed there 