Au pair agencies UK

I am looking to work in the UK as an Au pair and wish to sign up with an agency. However, I'm finding it hard to assess which companies are legit and which ones are scams.
I'm considering Global Work and Travel Co., but when I googled I found a few people who said that it was a scam company who ask for large amounts of money but do not provide the services they promise.
They seem to be pretty legit so far, except that the deposit they're asking for seems a little on the large side, but I was wondering if anyone's had any trouble or anything with them before.
If so, does anyone know any other agencies or websites that are worth checking out?
Thanks
-G

Getting a visa to work in the UK isn't easy, if you need one to work here. If you don't live in the EU it's only a very small category of people who can get a visa to work as an au pair. Otherwise you need to have special skills that are in shortage in the UK.

It's a concern that this isn't emphasised on the website as it would be a waste of your money if you paid and then found you couldn't get a visa.

A lot of people lose money because they don't know the rules, and paying money won't enable you to get round them. Make sure that you know whether or not you can get a visa before you pay out anything.