I have no direct experience with taking staff on, but whatever you pay them will determine the kind of worker you get.
if you are going to guarentee, 35 hours it needs to be sufficient for him to live off, and small enough for you to mke money.
It will also depend on how well your work is priced.
You should be able to get through £150 a day on your own. An extra man will bring in £100, you would then need to pay him £60 for the day, over 8 hours that would be £7.50 per hour. If you pay less than this, you will not keep staff.
presuming you pay someone £7.50 per hour 35 hour week = £262.60.
You would then be responcible for his Tax NI etc, I dont know the figures but probably £75 per week. Plus agreed holiday pay.
The first question you need to ask yourself is do you have the work.
If you get someone part time you would still have to pay them a reasonable rate.
You could sub-contract, but this will cost you more than £7.50 per hour.
It would be good if you were more candid about your situation.
Be specific with the amount of work you have, how many hours per week you work, the reason for taking on staff, you will then get plenty of replies.