Dear Mike,
Don't rush into this.
Firstly you will have to comply with the requirements of the Regulatory Reform (Fire Safety) Order 2005 from October this year. (I assume you are in England and Wales - NI and Scotland will have similar needs as well.) You will need to carry out a risk assessment of the church according to the 'Places of Public Assembly' guides - the Small/Medium one if your church has a capacity of less than 300; the Large if 300+. (See
www.firesafetyguides.comunities.gov.uk)
Secondly you only need alter your system if your risk assessment shows that the present one is inadequate to give everyone in the building a clear warning of fire.
Thirdly there will be advice available from the Churches Main Committee later in the year.
Looking at your description of your building, you need in brief:
A manual alarm call point at every exit;
Consider detection for any area where a fire could develop unseen and possibly affect an escape route;
ensure the alarm is audible in all areas when they are being used - eg when music is being played;
add flashing beacons so that anyone with impaired hearing is made aware of an alarm.
I assume the alarm system dates from the construction of the building, which makes it twenty years old or approaching that. The control panel will therefore be at or near the end of its life of circa 20 years. There will be advantages in installing a new alarm panel in terms of reliability and easier servicing, but the wiring may be adequate and not need renewal.
Re the emergency lighting - you need to ensure that all escape routes and any room without natural lighting is equipped at the very minimum. You may also need to improve and update exit signage - all these points need to be considered as part of the risk assessment.
If you are an Anglican church, don't forget you will need to take alterations through the Faculty process.
Hope the above is is of help to you.
