Most of London doesn't have catchments, and it's all done on distance.
But for the few schools which do (criteria will be along the lines of "siblings in catchment, then all other catchment, them other siblings, then all others) then you stand a chance, but if the school tends to fill up with "other catchment" at about the 0.5 mile mark, then no you won't get a place. Living in catchment isn't always enough, you also need to look at the actual footprint of "greatest distance offered" to assess your chances.
In London, you get 6 slots on your farm. So put the school you like best at the top, even if it's a long shot. You have plenty of spaces left for "bankers" (schools you are as sure as you can be you'd get an offer from).
It doesn't matter where on your form you list each school, as admissions must, by law, be on an equal preference basis. So whether or not you get an offer from the school you put in second place must be based solely on how well you fit its criteria (where is is on the form is not a permitted criterion)
The only time your preferences are taken in to account is if you qualify for more than one school. In which case the single offer you receive will be for the one you listed higest on the form.