Questions about hiring a nanny/housekeeper

[Longines]

We are looking to hire a nanny/housekeeper and have some questions:

Holidays:
We are away for about 5 weeks every year. The nanny/housekeeper wouldn't have to come in to work those 5 weeks. (We would of course pay every week of the year regardless whether we would be here or not.)
How many days holidays would a full time nanny/housekeeper be entitled to?
Would it be normal for the nanny/housekeeper to book her holiday when we are away? Or would she book her holidays totally independently from our plans?

Pay and hours:
What is the going rate for full time work and how many hours would this be? We need quite a lot of hours up to 55.. (We are based in central London. Our kids are 6, 4 and 18 months. Two of them are in school, the baby will start nursery later this year)

We would really appreciate some input into this, as I noticed there is a lot of variation in conditions...

Assuming UK, legal minimum is 5.6 weeks for a full time employee. You can give more than that but not less.

You can legally dictate when all your employees holiday is taken.
Not good for employer employee relationship though.
Some time they will take off will naturally be the same as you but they may want time off at other times. You will need to decide on each occasion holiday is requested if it is something you can cover, or not.

Pay and hours will vary. Being live in or live out may make a difference.

I can quite imagine central London nannies getting 15 an hour, working 60 hours a week. Though expect not everyone would get that.

Look at other jobs in the area.

Look at how much you can afford to offer. Work out all the costs as best you can. Don't over stretch your budget as you need room for unexpected costs and for things like a pay rise in future.