Depending on the role maybe a junior nanny would be the way forward or live in.
You'd be looking more around the £9-11 gross for live in and £10-12 gross for junior nanny I believe.
It's a demanding job with usually long unsocial hours, I've been a nanny for 10 years - I currently do 7-7 four days per week meaning I miss seeing my children before school and just get home to tuck them into bed over half of the week... I'm paid at the top scale or the job just wouldn't be worth it for me.
I also spend a lot of my own personal time usually weekends keeping my training up to date, planning activities and researching local playgroups so the 'job' doesn't always necessarily finish at the end of my working day.
Depending on your income you can also get help using the tax free childcare system, you can get up to £2000 per year per child and use with a Ofsted registered nanny.
Alternatively if the cost of a nanny is too much Childminder's are a great option, I've working as both nanny and childminder.
Depending where you are the cost varies massively, in SW London you'd be looking £7-9 per hour possibly more if it's just before and after school you require. But you then don't have the extra Employers NI and it's much less than the gross salary of a nanny plus you also need to leave kitty money for a nanny.