You say you wouldn't use a nanny yourself OP because you've seen too many bad ones... what do you think are the "red flags" that parents should look out for during interviews?
This is a really great question.
First, I would pay really close attention to how interested they are in the child/ren. Are they GENUINELY interested in them, or are they putting on a show? A decent nanny shouldn't care about you, your job, your hobbies etc. only about the children. Always do two interviews (at least), and always do a trial - try before you buy!
Have any of the families you've worked for, excluding Royals, been super famous, ie we'll have all heard of them? Yes. Several.
Also, which countries would you love to work in and why? Hawaii, I don't really know why! Scotland would be awesome. TBH I don't really care where I am at the end of the day, so long as the family are decent.
What is the most demanding thing a child has asked of you, same question for a parent. Child - not a lot. Because I'll say no if its unreasonable and as I haven't done it, I can't remember. Parent...Jesus. Thats a thread in its own right actually it is anyone remember the Swiss Nanny thread? I once had to wash all of my (clean) clothes, ALL of them, twice because they didn't smell of the right detergent and Mum wanted baby to smell only her.
What are your quarters like? Usually nice. Seperate apartment a lot of the time. At the very least a bedroom with ensuite. No horror stories for this one.
Top 5 gifts you've been given. Designer Clothes, Designer Perfume, An iPhone, A car and, not me, but one of my friends got given a Saudi Princess's bed!
Most expensive gift you've been given. The car.
Most OTT gifts parents have given children/most spiky moments. Diamonds. Actual, real diamonds handed to toddlers as presents during Ramadan. FFS, still makes me cross (the dirt poor, 24/7 working maids who earn pennies an hour had to hand them out 
)
Op, do your current charges know you are going? Did you resign? How long were you there for? No, they thought I was going on holiday. The parents always make me lie. I was made redundant on my last role, through no fault of my own but if I were to explain it'd out me probably. I was there for 7 months.
You say you don't have any special training or qualifications but the two girls I know working in this area of the sector all have extra skill sets, speak three languages, ski, horse ride, have close protection training, sailing qualification etc etc... They say it is absolutely expected and most jobs specify these things.
I don't doubt you're genuine but how arw you able to get these jobs when the industry standards appear to not match your qualifications?
I've been nannying for a fair while so have a good CV behind me, I'm also "very English", with a well spoken accent which I think helps enormously. Without sounding like a complete tit, I present well - I've been told I come across as very intelligent and very calm. I typically don't care about people's status or wealth, and I'm very laid back and I think that comes across at interview. A lot of highly qualified nannies, particularly Norlanders, in my experience come across as cocky, demanding or very rigid/inflexible - and families prefer a calm, laid back personality. I can only speak from my experience though.
Having said that, I'm 26 years old - I have travelled to 22 countries, own 3 businesses, can play the piano, ski and horseride, am a member of Mensa among other things, so I guess this helps. But no actual qualifications beyond A-Levels (not in childcare related subjects), a paediatric first aid and a clean driving license.
I honestly think its down to presentation. And my salary is so high because thats what I expect. People will value you how you value yourself. Do I believe that what I do "deserves" or "earns" £110, £120, £130k? No, not at all. But I expect to get paid that and that "confidence" comes through and puts me in that price bracket. In reality, I think as a person I'm pretty damn worthless, but I'm confident in my knowledge of the industry and my place within it. I hope that makes sense? It's late here and my brain isn't working well.
What kind of toys do the children have? This is generally the same for most families;
Step 1: Go into Harrods
Step 2: Go upstairs to the Toy Kingdom
Step 3: Buy everything. Twice.
We are talking miniature cars. WORKING miniature cars that they can ride in. Lots and lots and lots of crap as well.
I have several years of VVIP nannying in my past... I had a paediatric nursing degree, but no other childcare qualifications and I found work extremely easily via the right agencies.
I was only ever once interviewed by the parents - in all of the other placements I was interviewed by the family PA or current nanny although I did get to meet the parents before I started in most cases. One of my jobs I was recruited through word of mouth as an emergency placement as the current nanny had to leave for a family emergency and I started the role (and sole care of the 2 DCs) before I'd even met the parents. The nanny was told to find her replacement, and she did!! I wonder if this sort of practice still happens? I certainly used to come across the same people (though most staff are dispensable and could be gotten rid of at the drop of a hat)
I also only had 2 interviews in the UK - the others were all overseas (I was flown to the destinations). Has this changed much over the years?
That's exactly my experience of it!