Last year I came across an English-speaking church here in Bielefeld.  It is a Protestant church.  Here is the information:

International Baptist Church Bielefeld- Flensburger Straße 2, Bielefeld, Germany
Website: www.ibcbielefeld.com
Depending on where you are living in Bielefeld, it may take a bit to get there using public transport.  Sermons are given in English on Sundays at 10:30am.  The  congregation includes people from all over the world.  Childcare and Sunday School are available for kids.

Patty