Pension - working tax credit

I have a question if anyone could answer, I work part time 16hrs a week and claim WTC and I get the disability element .I have two small seperate pensions from when I was self employed I want to cash in the least value one. I know I will pay 25% on it the rest i'm not sure as I earn only £6,500 pa my tax code being 1150 with the pension and earnings come below 1150 would I pay tax also would my tax credit be reduced because of this cashing of my pension Thanks in advance for any answers.