SCAM - do not respond or send any personal details. if you have change your email address as you will now be scammed by others
There is no Caribbean Travel in Marylebone. 14 Marylebone High Street is Ponti's Cafe, not Caribbean Travel
If you are not an EU citizen there is no way for you to be employed as a nanny in the UK. The Au Pair visa was cancelled in November 2008 due to the oversupply of EU childcare providers and high unemployment in the UK
http://www.ukba.homeoffice.gov.uk/workin…
The only non EU citizens who can work as nannies/au pairs are those from a country on the Youth Mobility Scheme - Canada, Australia, New Zealand or Japan
Travel agencies in the UK cannot process work visas. All they can do is book flights, hotels, cruises, etc. If this were a real job offer, your employer would file all papers with the Home Office and pay all fees. You would then be mailed (never emailed) a letter from the Home Office instructing you to make an appointment at the British Embassy near you to get the visa stamped in your passport.
Anyone asking you to contact anyone but the UK Home Office or British Embassy is scamming you
Nanny scams are one of the most common Nigerian scams. They trick you into paying non-existent visa fees to a "travel agent" or "lawyer". If you are naive enough to pay, they'll ask for more money for some certificate. If you pay that, they'll ask for more money until you finally realise you've been scammed
Just google "nanny scam" and you'll find over 900,000 hits.