Atqui to answer your question as best I can I am not an ex-Christian, but I am an ex-churchgoer and to some people they seem to be the same thing:
I became a Christian after reading a bible gifted to me by a Roman Catholic acquaintance. Prior to that my experience of church and the Christian religion was very limited. I grew up under the influence, in my teenage years, of my communist father who I would now describe as a militant atheist. In the early years of my newfound faith I was very much a traditionalist although I was never tied to a single denomination - I simply attended my nearest Christian church. I gained various leadership positions and taught Sunday School for close to thirty years. During that time I continued to learn more about the faith I professed and my husband and I together challenged and questioned the orthodoxy of traditional Christian teaching. Eleven years ago we left the church where we held leadership positions to pursue a simpler, more holistic expression of our faith. Now our faith is primarily worked out in community action, but we meet together often with like-minded Christian believers, in a home rather than a church building, much like the early 'church' did before it became an institution. Some may think we have lost our faith because we don't 'attend' church any more, but I think it would be true to say that we are now more 'church' than we have ever been. People find it hard to understand what we're doing so we end up describing ourselves as simple church/house church/a fresh expression of Christianity etc. but really we're just a bunch of pals who get together to enjoy each other's company; we talk about life, we pray together, we ask questions and we don't always agree on the answers, we encourage each other - and we eat together. Happily the more traditional Christian minister/vicars do 'get' us and we feel very much a part of the wider church here in our town.