I have one night babysitting a week included but they rarely use it, it usually gets used when the trains/tube is running late or MB gets held up at work for 5/10 minutes. Never for an evening out!
If you don't need babysitting included (you are home on time every single night) then you could pay less and then pay an agreed babysitting rate if you need her to baby sit.
I would advise a 5/10 minute hand over both morning and evening, if you need to leave at 7am and nanny arrives at 7am, you'll be charging out of the door as soon as she arrives. Same at the end of the day, if nanny finishes at 6, she'll want to do her own thing at 6, not hang around for a chat about the children's day for 10 minutes. Also, if you are not going to be home on time, do not inform nanny at home time that you are going to be an hour late, if you need to leave work at 5:30 to be home by 6:15 so nanny can finish at 6:30 then let her know as soon as you know you are not going to get away on time and give her a rough eta and keep her posted. It's not like we can just leave at clock off time. This is a huge bone of contention for most nannies. As is not being paid on time! If you can get home early, let your nanny finish early! This will give you a nanny who will go the extra mile in regards to staying late if you let her go early occasionally. We are much more likely to be flexible if we feel respected.
Do not leave washing up on the side/in the sink and the dishwasher full whether clean or dirty, we are employed to look after your children, not clean/tidy up after our employers. Same as keeping the areas nanny and children use clean and tidy, if nanny leaves things clean and tidy at the end of the day/week, make sure it's left the same in the morning, especially Monday morning. However, you can expect nanny to leave the house as she found it in the morning.
Using the kitchen/family areas when she's not working - be clear about whether you are happy to come down for breakfast in her (decent) pyjamas and join you or if you'd rather she waited until you and the children had finished and tidied up (my charge is a little monster when he has more than one adult joining him for meals!) and the same for evening meals (I eat with my charge as my employers eat far too late for me) if you are happy for her to join you then let her know, if you'd rather have cooking/supper time for catching up with your other half then ask her to eat earlier. If you have a spare reception room/playroom you could put a tv in that would be nice for her. Going to your bedroom at 7pm is pretty sole destroying!
Re my wage - I have been a nanny for 30 years (in 4 weeks!) and I have amazing references. If you get a younger nanny with less experience you won't have to pay so much.