Few bank holidays fall during term time - for example, this coming monday falls during half-term... least it does for the children I nanny.
I think it works like this:
The holiday is calculated on an accrual basis, that means that for every hour worked a small proportion of holiday is earned. 5.6 weeks? holiday, divided by 46.4 weeks (being 52 weeks ? 5.6 weeks) multiplied by 100 = 12.07% This gives you the multiplier figure to use to calculate holiday entitlement. Whilst on holiday you don?t accrue holiday.
Is term time 40 weeks? I suspect it varies from area to area and indeed school to school. So figure out what the weeks would actually be for this year and next if you have the dates available... check that it's the same, or use whichever is the higher figure.
So if the nanny was working say 10 hours per day, 5 days per week, 40 hours per week, then working hours per year would be: 2000
Holiday entitlement: 12.07% of 2000 = 241.4 hours. Round up to whole hours = 242 hours.
If a bank holiday fell during term time, such as May Day which often does fall during school term time, then that day could be taken as holiday, using up the usual number of hours worked on a Monday, so 10 in this case.
"Holiday pay should be paid for the time when annual leave is taken. An employer cannot include an amount for holiday pay in the hourly rate (known as ?rolled-up holiday pay?)." Source: Gov.uk
So if they are not working half terms, they take that as holiday. That could be 3 weeks... so 15 days of holiday, or 150 hours in this example.
Holiday may be taken at the end of the term - some schools finish on a Wednesday or Thursday, rather than doing full weeks, so there may be some days at the end of each term which can be taken as holiday.
I feel you need to agree on the number of hours holiday that they get paid and that they are to take that holiday when convenient, which is days that the children do not go to school such as during half term and longer school holidays.
If you are happy for them to take the occasional day off during term time, that's fine.
In your case as it is an after-school nanny the hours per week will be less but the principle applies. 12.07% of hours worked is the holiday entitlement and you can not add that onto the hourly pay rate... they actually need to take it during times like half term.