My lo is with Kids London. She has just had her first job confirmed today, but has been with the agency for 4 months! I'd really recommend having a look at the baby and child modelling thread on the netmums website. There are loads of mums with baby and child models on there and they give great advice. There is also a list of agencies and what they look for on page 500. http://www.netmums.com/coffeehouse/lifestyle-8/join-club-95/45982-baby-child-modelling-club-577.html
Hopefully this will work if you copy and paste, I'm rubbish about putting links in.
xx