can you not take on a person as a sub-contractor and let them be liable for any mishaps they have, you have no written contract of employment with them,
also take some one on as them being self employed as above, making them liable for any work related issues.
if you are a one man band and get extra work on, and you find it a minefield to just take someone on for a couple of days a week, what would be the best outcome for yourself to cover you from any mishaps the chap has, injury or sickness they ocur..
As in Scaffolding, a lot of scaffolders are actually Self Employed, even though they are with big companies.