Hi there,
I was in Mothercare today and I saw these at the till http://www.mothercare.com/Sock-Ons-Girls/dp/B001QV9J2M/sr=1-4/qid=1243267284/ref=sr_1_4/275-3183909-3364541?_encoding=UTF8&m=A2LBKNDJ2KZUGQ&n=42764041&mcb=core
Now I haven't used them as my LO is 2 now, but the lady on the till said she's had a number of people say they are brilliant. They go on over socks to help keep them on.
They might be worth keeping in mind, and if I have another, I'll certainly be trying them
HTH