Eddie your figures appear way off the mark, are you saying you are paying £1200 for your van insurance and spending £100/month on gear, if so then you need to shop around.
Obviously the more staff you take on, the cheaper the individual costs are.
You have wages down as £2000/month (£24K PA) what are you basing that figure on.
Employing staff is a big decision, a big responsibility, and often a big headache, however it can also reap big rewards and gives you security for the future.
If you are self employed, working alone and you break a leg or worse, unless you have very very good health cover, you will not be bringing anything in. If you have staff working for you they are constantly bringing income in to the business, whatever you are doing.
The subcontracting works, but only to a level and you would always be looking over your shoulder for the Taxman catching up with you. If you are going to do it, do it properly and take them on the books.