You can always calculate it yourself?
Working tax credit is made up of basic (£1,920 from April 2010), lone parent element (£1,890 from April 2010), and 30 hr week element (£790 from April 2010), plus childcare costs (80% costs up to a max of £175 per week for one child).
This is then reduced for 39p for every £1 you earn over £6,420.
Therefore assuming you work full time with no childcare costs (as I can’t really guess) you would get £1,920 + £1,890 + £790 – ((£18,000 - £6,420) x 39%) = £84.
Child tax credit is made up of family (£545), baby (£545 if you have a child under 1), and per child (£2,300). It is reduced the same way as WTC.
Therefore you would get £545 + £2,300 – ((£18,000 - £6,420) x 39%) = £nil. However there is a minimum CTC for families with income under £50,000 of £545. Therefore you should get that.
So only £629 in total, but this will increase once you have your second child.
The tax credits for 2010/11 will be based on your earning for 2009/10, but you need to tell HMRC of any changes, ie: being back in work. However unless your income increases by over £25k, the income increase will be ignored for one year. Thus you should still get 2009/10 amounts for the next year.
Hope that is helpful! You can check the relevant current year rates and thresholds at:
https://www.hmrc.gov.uk/rates/taxcredits.htm
