if you are not a church leader/treasurer then its unlikely that you will know of the challenges presented to us in negotiating with potential ISP's specifically as potentially a business or charity
In this case, your church will be treated the same as any other CIO. I am a trustee of a secular CIO with a multi-million annual turnover, and previously served as a trustee of a national church body established by an Act of Parliament that is a registered charity.
Most ISPs will treat your CIO the same way as any other business, and your church will typically be treated the same as any other business premises. FTTP might attract additional construction charges, depending on the nature of the building.
You would probably be best off speaking to the SME team at a few more business-oriented ISPs, though I suspect they'll offer you their standard small-business product at the regular price.