Hi. I am a nanny and have been for several years! Good luck in finding someone great...
"Nanny will be contracted to work until 7pm, but what if me and DH are held up at work. Would I pay her time and a half? And, what happens if I was 15 minutes late? or 10 minutes late? would I pay for whole extra hour?"
IMO this is a give / take thing - so long as you wouldn't mind if the nanny needed to leave 15 minutes early sometimes if it suited you, I don't expect any overtime in these situations...
"Babysitting (which would be agreed in advance) - would I pay her same daily rate, or would I pay her higher rate?"
I get my daily rate..
"Bank holidays - I was going to pay her, but only for hours she would normally work eg. if she would normally work 11 hours on Monday, I would pay her 11 hours on bank hol monday. But I would only pay her 3 hours for good friday as she would normally work 3 hours"
Sounds fair...
"I want her to keep a basic diary - what DD ate, how she slept, poo and what activity they did."
This can be quite simply done, I plan in advance my menus / activities/ play dates in a diary kept by my family, so I can shop / plan for them accordingly, so this is really no extra effort to share with my MB/DB.
"Also, to take photos of anything new DD experiences ie snow. - This isn't asking too much, is it?"
No it isn't, and I tend to WANT to share this sort of thing with my employer.. I find it exciting when the child tries something for the first time. I am often texting my MB pictures of her children doing something cute I've snapped on my phone
"I'm going to operate a kitty box - would it be too much to ask for receipts for travel and mobile phone top-ups? (It's not that I don't trust her, but might be able to off-set against tax)."
I automatically pop change/receipt into our tin, despite my family's insistence I don't need to show what I've spent.. It's no trouble at all. I am automatically quite frugal / sensible with the money as am conscious it isn't mine... You best explain about the tax thing though, if I thought it was to keep tabs, I might feel offended.
"Also, have been wondering what to do about cheque books and credit cards which I don't keep under lock and key, but are in the drawer of my desk. Ordinarily, I think I'd just have to trust my nanny not to rifle through my things (as I'm trusting her with my dearest DD). However, dearest DD has taken a liking to emptying this drawer and so my nanny would have to put all my bank stuff back. So, would it be best to put it in my bedroom, which will be an off-limits area?"
I often use my MB's credit card, she has given me permission to do so obviously. I also sleep in her bed when she and DB are away. Just as I don't mind her kids being in my bedroom at my place, whenever they stay there (littlest loves sleepovers with me!!). We are very friendly though, You might find once you meet your nanny and get to know her you won't feel so worried about this point.
Good luck and hope this helps!