Your employees should have a contract of employment when you sign them up and this should cover holiday entitlement. As far as I am aware they are entitled to 4 weeks holiday per year plus bank holidays.
You cannot contract your employees to 7 days a week, you can contract them to 6 days a week with the seventh day optional, so if his contract is 6 days x 1.5hrs then that is what his holiday pay will be. (one days hol = 1.5hrs).
Not sure exactly what you are asking about sickness, but if it is regards pay, you do not have to pay them sick pay and they are not entitled to anything for the first week, but after this they may be entitled to SSP (you pay the SSP entitlement and it is deducted from your PAYE tax returns) your PAYE pack will explain the ins and outs or if your payroll is done by an accountant then he will do this for you. They must fill out a self certification for the first week and a doctors note after that. SSP calculations can be as complicated as PAYE deductions. So as daunting as your PAYE pack may be you need to read it and understand it. Failing that employ an accountant to do your PAYE, this will ensure things are done right.