Sorry, I've employed nannies for 14 years in London and I would not consider you as a nanny after just that level of experience and with no nanny qualifications. I think you would value brutal honesty so here it is:
One one year job and one two year job, one of which was more like a mother's help, doesnt make you an experienced nanny but more like an entry level nanny. Your first job sounds like it was pretty exploitative - long hours, lots of kids, no experience, so I would not be terribly impressed by the reference from that family - am sure they were lovely in person but as a potential employer I would suspect they were just looking for cheap childcare and not as picky as me. I am not saying this would be true of them, but just that would be my fear as I looked at it and I would discount it.
Totally agree with the comments on written english.
Also you wouldn't pass my 'cooking' criteria with 'pasta soup veggie bakes' - I want fresh meat, fresh fish, proper healthy cooking.
Wouldnt look at anyone without CRB and currrent first aid certificate.
Do you drive? You don't say, but its essential in London for anyone other than toddlers.
I would worry about the fact you mention you are studying accountancy as it would make me think you werent committed to working with children - my nannies are all professionals, with qualifications, and all they want to do is work with children. They have gone on to other jobs but always children related.
Culture? Don't know enough about Romanian culture but I always ask non-English nannies about their child-rearing culture - i am generalising wildly here but I have found there are some countries where the culture is too different from the way I bring my kids up and so a nanny from there and I would not click. Never interviewed a Romanian so no idea on your culture, but if it is different from the liberal north london one might be worth reading a couple fo good books so you can show you share the same values about child rearing.
So perhaps look for people with one young child, where you can grow in your experience with the child. Trouble is, those employers are more likely to want a cheaper live in nanny - when I switched to using live out nannies it was because I wanted much more experience, and so was happy to pay more. I don't think the salary you are looking for is ridiculous for a live out nanny, but you would be one of the least qualified or experienced live out nannies i would ever have come across and i wouldnt give you an interview. I think your problem is you are putting yourself out as a live out nanny and realistically you just arent experienced enough - I think you have more of more an 'au pair plus' CV and so recommend you look for those roles, which will pay more like £350 per week than £450 per week.
HTH - suspect it's unwelcome but it's honest.