You have to work at least 16 hours to get working tax credit, you should also be entitled to child tax credit. You can estimate how much this will be online if you fill in questionnaire on www.hmrc .gov.uk. I think your income support will stop, you should still get housing benfit but the amount may change. If you are worrying you will not have enough money for a month you can have your tax credits paid weekly. Also a tip with tax credits, is make sure you keep all corresponda]ence in a folder and inform them immediately of any change, then make sure you get written confirmation of the changes!
hope that helps x