26 per week... is that 26 hours per week?
How do nannies get paid?
Usually via direct payment into their bank account these days.
You are an employee so your employer agrees a gross salary with you, they run PAYE which means they deduct income tax and employee national insurance and pay those on your behalf to HMRC. They as employers pay Employers National Insurance to HMRC.
Have a play with this PAYE Calculator. Enter in number of hours, number of days and gross pay per hour or per day or per week. See how the figures change with different gross salary.
Not sure what your taxcode would be but keep it as 944L in that calculator. Once payroll is started HMRC will assign you a taxcode if they don't want the employer to use 944L.
When completing your self assessment tax return you would enter figures for what salary you had been paid in other employments.
Payment is usually at the end of the month, so paid after you have done the work.
what happens if you are not needed during school holidays as regard to payments?
Depends on the contract. It is possible to have a term time only contract.
You need to consider if such an arrangement would suit you or not. Also you would need to consider if you would agree to taking all statutory holiday entitlement during school holidays. The family will need to pay you for days when you take holiday. Calculation for term time holiday entitlement is a bit more complex than for someone who works all year. You get 12.07% of time worked as holiday.
Who's responsibility is it to pay for public liabilty insurance/business car ins?
It would be your responsibility. You will need to contact your current childminding insurance provider to see if the existing policy covers it, or if you need a new policy. Motor insurance should be the same as you currently have, though if you brought via a brooker such as MortonMichel do give them a quick call to confirm.
what if your ill and cant go into work or they are sick and don't need you?
Statutory sick pay if you are ill. It does not start until the 4th day of illness. So basically you don't get paid if you have a day off, though many employers of nannies will look at each event and decide if they will pay or not.
Parents can't just decide they don't need you. They produce a contract that states your hours per week and salary, so they need to pay that regardless of them not wanting you to come to work. There is provision within employment legislation to lay-off staff for temporary periods but I won't complicate things by saying more about that, nanny employers would not usually use that provision.
Keep in mind that the family decides the salary, not you. The family provide the contract, they dictate the terms of the agreement. You work for them, do as they say. It is not like childminding where you have control over what you do.
There are various nanny payroll companies who can assist employers of nannies. I do suggest that parents at least talk to a payroll company, even if they do not decide to use their service, as the payroll companies will often provide quite a lot of advice about how to get things started.
Are you in England? Will the family need you to be Ofsted registered?
If so, check with Ofsted with regard to what you need to do with regard to your current childminding registration. You may want to keep it going a while, rather than changing to being a Home Childcarer. Ofsted I suspect will permit that for a while, though I would have thought that it would be wise to let them know that on x days you are a childminder and on y days you are a home childcarer (and give address of the family for whom you are nannying).