In my capacity as almost tame risk assessor type person, I came across a useful document on fire risk issues for 'small and medium places of assembly' - which includes churches.  It is downloadable free - or you can buy a real copy for £12.  It's quite a big thing to plough through, but for all that it is in normal English, and has some pictures!

Should you want to check out, for example stuff around room occupancy, how many fire exits you need or how your chairs need to be fixed together, it is helpful.  Not worth losing sleep over, but at the same time helpful for those odd occasions when you need to cram people in (when I checked retrospectively the needs for our carol event last year I found it was compliant because it eventually becomes intuitive and is, at the end of the day, just good old common sense).

Anyway, if it is helpful take a visit here or, for other issues that might face you and your church check the main website here