Paul. you don't need to know how many house in an area only how long they will be leafleting for, they will need 250 leaflets for every hour, this is too many but it means they won't run out.
I employ my own leaflet deliverers, I have them work 2 hours a day the same hours every day. My lads work 3-5 I don't back check but I call them 2 or 3 times a week and ask where they are and visit them. they know if they are not out and they have not informed me in advance they will not be working.... they are sacked.
i use google maps and make them work in the area they live so they never need to travel more than 15mins to the target area( I don't pay travel)
if they don;t live in the area they don't get the job,
i vist them on a Sunday and give them the leaflets and pay them