Tax credits

[Mo J]

Hi All
Calling all working mums, whether you're in full time or part time.
At the moment I get around £50per wk Family Tax and £10 per wk Working Tax. And am on Maternity Leave.
I am starting a weekend job next Friday as don't want to return to work full time. It is 16hrs per wk.
What I need to know(if you can help me that is) is, am I still entitled to any of that money? Or would I lose it all? Or do you reckon I'd lose much of it?
I'm really good on Maternity Pay, but c**p on Tax credits.
Thanks for any help