You're optimistic, blondes! It was nearly midnight for me when you said that and I was sleeping!
Nicks linked to the list but there are a few main quals with their pros and cons.
NNEB (old style) - good blend of theory and practical placements but nannies with this will probably have a shedload of experience anyway
DCE (replaced the NNEB) - same structure pretty much but less acapdemically rigorous and some useful skills got dropped in favour of legislation aspects. Still an excellent qualification.
BTEC diploma (NB first certificate and certificate are a lower level) - very similar to the DCE but more academically focused. Still a lot of practical work but accepted as equivalent to 3 Alevels by unis for childhood related degrees.
NVQ - vocational based training, often done in a nursery. If you have someone who's done this as a nanny then you know they've been assessed and observed as a nanny, not as a nursery nurse or childminder - the assessment is different depending on the position.
Those are the most common level 3 qualifications which is generally accepted as desirable for a nanny.
You may also get CVs with a BTEC certificate, CCE or NVQ2. These are roughly equivalent to the first year of a level 3 and are billed as suitable for someone working under supervision. That said anyone with that and some experience would be fine as a sole charge nanny.
The minimum I would expect is the ICP or MNTs core skills course for OFSTED registration.
Going the other way you can get nannies with a level 4 cert in early years, a level 5 diploma or a full degree in early years or childhood. These nannies will be more clued up about theories of child development and national frameworks but it's not necessary IMO in a nanny! They often charge more too - so if I were getting a degree qualified nanny I'd get one with a degree in a different subject that had value added (like music [biased emoticon]) on the assumption that someone with a degree wanting to be a nanny has done some research into children and has experience! Degree educated nannies tend to value education quite highly which can be a good option for older school aged children however with a little one, unless they had short courses or significant experience with under 1s, you're probably better off with a level 3 qualified nanny who has a good broad base with plenty of supervised practical experience.
Less common are qualifications in preschool practice or playwork or Montessori method. Again no reason why they shouldn't make a perfectly good nanny but not as thorough as the traditional level 3s. You may also get people with bolt-ons like the MNT maternity practitioner award. Not a nanny qualification but does demonstrate commitment to childcare and continuing development. Also at level 3 but not broad spectrum - it's focused on newborns.
One to watch out for is the diploma in home based childcare. It's a real qualification, built on the ICP, but it's aimed at childminders with nannies bolted on so very heavy legislation-wise and goes into detail on observations and the national frameworks for EY education. No actual practical work with children is needed, there's no vocational assessment element and I would thoroughly grill anyone with that because I think it's a fundamentally flawed course.
I would also be wary of anything done via distance learning, even if it's edexcel or another exam board. The qualification may have expired but still be offered by a distance learning college. the NDAQ is your friend here
Far more important are the qualities nick mentioned - especially common sense - and experience. I wouldn't screen CVs based on a qualification unless they had less than 5 years experience as a nanny or had only worked with 1 age range. The biggest benefit of a qualification is they will have covered at least in theory, but probably also on placement, children of all ages and developmental stages. A nanny with 5 years exp may have had 5 1 year positions with 2-3 year olds, or 1 5 year position with a 3 yo and a newborn at the start. If neither had a qualification I'd be a lot more confident leaving children with the second as the first may never have dealt with a child outside that narrow age range.
sorry for the essay.