I think you have three types of Worker and you need to work out which one will suit your way of working and your expansion plans.
1) The person who has a family to support, needs to work hard to make a living and wants to work. Looking for job stability and a future. If pay these workers a minimum of £100 a day and would have no qualms about letting them have their own van and even full management of their part of the round. Easiest way to track them down is to advertise as a yearly salary and interview well, digging deep into employment history and family situation. You should have no trust issues with leaving them to run the show while you are on holiday..
2) The floating worker isn't in it for the long term will get bored quickly and tends to drift from manual labour job to manual labour job. Ideal two have two or three of these part time working two or 3 days a week due to reliability issues. Pay them £60-70 a day Find out what pub they drink In and drop in a couple of times a week to see them spending all of their money in the bar.
3) young lad/ Student- ideal for summertime school work and weekends, always good to have no formal arrangement with these as they will let you down. Get them to call you when they need a week or twos work but try not to have them for any longer. When they call put them in a an with employee type one or yourself and employee type two and just use them to get ahead so you can have a holiday.