MagicOC I think MNT used to run the ICP course which was for CHILDMINDERS but they were using it as a means of getting nannies registered. What course did you do with MNT? Has MNT given you any documents published by Ofsted which state that NANNIES (not childminders) need to have Policies & Procedures documents signed by parents. The only one of which I am aware is Medication and that's an Insurance requirement, not an Ofsted one.
If you have found someone on Ofsted's website, then point me to it, but until then, Ofsted can not tell nannies that they should have that sort of signed permission. A nanny is an Employee - their written statement/contract could well cover that sort of thing.
This sort of thing I feel is between the parent employing the nanny and the nanny themselves. Any involvement from a childcare regulator I feel is wrong, as nannies are not regulated... they are purely registered for childcare voucher scheme/tax credit purposes.
gobblygook - if you don't want your nanny taking photos of your son, then as the employer you can dictate that. However photos are a good record of what your son has done, so can help show you some of the things he does during his day. Suggest they use your camera perhaps, though that means another thing to carry around with them (does your nanny have a MaryPoppins bag) and potentially lose. May be easier to purely ask your nanny not to share the photos with anyone, including their partner but instead to send them to you on a regular basis... I try to upload weekly, though it can sometimes take a bit longer than that.
You should also consider photos of your son being taken by anyone else. If they go to a SureStart group, then a permission form may well need to be completed to permit (or not) the group to use your son's picture for display work and in the media. You can't stop someone else taking a picture of you on a public street. Your nanny could tell friends that they can't take pictures and they should honour that.
Try to focus what your concern actually is - is it to do with photos possibly getting onto a site like Facebook, or is it that you are feeling that your nanny is having a closer bond to your son that you had thought they would, or if it's something else.
The photos I feel should be for work purposes, they are to document the things they do during the day. Some weeks you may get quite a lot, other weeks you may not get many.