Alterations to a church hall fall within the normal planning and consent process. For example, if a church hall is a designated listed building, it will require listed building consent from the local authority for any works that affect its character. An unlisted church hall may also require conservation area consent if it is in a conservation area and changes such as cladding, inserting windows, installing satellite dishes and solar panels, adding an extension, laying paving or building a wall, are carried out. Contact your local authority for clarification and before starting any work.
Very rarely, a church hall may be attached to a church. If this is the case, then normal faculty rules apply.
Also make sure you consult the owner of the church hall eg. the Representative Body, Diocesan Board of Finance, etc, before carrying out any major alterations.