Template Contract - this can be handy to use as a starting point for a nannies contract.
Holidays, Sick Pay etc are all the same as any other employment contract.
Currently Holiday Entitlement is 24 days, from 1 April 2009 it rises to 28 days. BERR.GOV.UK Holiday Entitlement Information
Sick Pay - SSP Info from DWP.GOV.UK
I would not suggest offering anything (in written statement/contract) better than SSP. If your friend was to say offer 5 days sick per year, then their employee could well take those days off, even if not sick.
With SSP in the contract, if the nanny is off sick and it is genuine and their employer is feeling nice, then the employer can choose to provide full pay on that particular occasion.
No, a nanny does not need to have the same holidays as the employer. Typically, with a full time nanny, the employer chooses 2 weeks, the nanny chooses 2 weeks. It is handy if the contract says how much notice is required for the employee to take holiday.
As your friends nanny is only working 2 days per week, holiday will need to be done pro-rata. So currently entitlement is 4.8 weeks - so 4.8 weeks x 2 days = 9.6 days.
Please make sure your friend has agreed a GROSS salary with the nanny, not NET (take home). Far easier doing payroll then.