I'd go for the "main use" approach: if it's essentially a civic hall that just happens to be used for worship (i.e. it's not the actual parish church), then it's `amenity=parish_hall`. If it's *the* church, but it's also used a lot for other uses, that's `amenity=place_of_worship`. Where I live, it's understood that most churches have an area that constitute a "parish hall", which can be rented for various activities (that area may in fact be the church itself!). I'd still tag them as places of worship. Remember also that "secondary" uses can be usefully covered by using a descriptive `building=` tag, and that in practice, *you can tag however use [any tags you want* like][1]* as long as it makes sense, so `amenity:secondary=` is a perfectly valid way to indicate it, even if it won't display on the map (but then *no double features* will ever display anyway if icons would be the mean to do it, and IIRC, there is no icon for parish halls).halls). [1]: http://wiki.openstreetmap.org/wiki/Any_tags_you_like

I'd go for the "main use" approach: if it's essentially a civic hall that just happens to be used for worship (i.e. it's not the actual parish church), then it's `amenity=parish_hall`. If it's *the* church, but it's also used a lot for other uses, that's `amenity=place_of_worship`. Where I live, it's understood that most churches have an area that constitute a "parish hall", which can be rented for various activities (that area may in fact be the church itself!). I'd still tag them as places of worship. Remember also that "secondary" uses can be usefully covered by using a descriptive `building=` tag, and that in practice, *you can tag however you want* as long as it makes sense, so `amenity:secondary=` is a perfectly valid way to indicate it, even if it won't display on the map (but then *no double features* will ever display anyway if icons would be the mean to do it, and IIRC, there is no icon for parish halls).