One of the basic principles of Christian mission is described by Paul in his first letter to the church in Corinth:
Though I am free and belong to no man, I make myself a slave to everyone, to win as many as possible. To the Jews I became like a Jew, to win the Jews. To those under the law I became like one under the law (though I myself am not under the law), so as to win those under the law. To those not having the law I became like one not having the law (though I am not free from God's law but am under Christ's law), so as to win those not having the law. To the weak I became weak, to win the weak. I have become all things to all men so that by all possible means I might save some. I do all this for the sake of the gospel, that I may share in its blessings.
1 Corinthians 9:19-23, NIV
Basically, if we want to reach goths with the good news of Jesus (for example), the best way of doing that is to give up all the secondary cultural stuff and become a Christian who is also a goth.
Otherwise, if you've got a bunch of Christians who are all (as many are in the UK) white, university educated, middle class, non-smoking professionals, then outsiders are going to look in and say "That's a place for white university educated middle class non-smoking professionals, but I'm a black brickie who smokes and left school at 16, so I don't fit in." It shows people that they can fit in, it gets rid of most of the barriers, and lets them see Jesus better on their own terms. It doesn't demand that they have to change all their cultural stuff, that might well define who they are, if they are going to become a Christian.
I'm a Christian first and foremost. Yes, I'm white, middle class, university educated, non-smoking. But that should all be negotiable (except it's hard to change my DNA or the past). It doesn't define who I am, so I can change it if I love other people enough and really want them to know Jesus.
Now here's where the rubber hits the road. I know of no Christian churches which are doing this in trying to reach Muslims. I don't know Christian churches where the leaders grow beards, the women wear head coverings, they sit on the floor and put the Bible on a stand, where they only eat halal food. And we wonder why so few Muslims in the UK become Christians! Isn't it obvious! It's because we're not making the effort - because we are holding too tightly to our own culture to bother trying to reach them. I'm not saying we should become Muslims; I'm saying that where issues are negotiable (like hair styles, probably not like gender roles) then we should be willing to compromise to reach others.
What do we do instead? Benedictine techno-trance (no offence to those who really love that stuff), but the C of E seems to plug loads of money into alt.worship stuff because it is trendy even though it seems to bear no fruit and they don't know who it's meant to be reaching.
I know some great fresh expressions of church. I've talked about some on this blog - I've got friends involved with initiatives like the Plant and Eden. But they work precisely because they are losing classic white, middle class, etc culture and changing their culture to that of the people they are trying to reach. Where are the Christians willing to become like Muslims to win the Muslims?