unlikely. You will likely have to change the base aswell. Even if you go for the same manufacturer, if theyre old old, the design will likely have changed.
Swampy,
Unfortunately the heads are not normally interchangeable. What is your current brand - it might still be on sale?
But you can normally replace the wire smoke alarms with new ones - but they all have to be the same brand/model of alarm.
All wired smoke alarms normally require four wire connections: Earth, Live, Neutral and Signal (the first alarm to sound, uses this signal wire to tell all the other alarms to sound).
There is a simple wire diagram here http://www.aico.co.uk/How-do-I-wire-hard-wired.html <<< this is not a promotion of these alarms, simply the first I found on Google.
Note that the smoke alarms are connected with "Three core plus Earth Wire". And many use the colours differently. So before you take down the old alarms make a note of how the cables are connected and their colour.
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