Looks like a standard Aico base (I think that's the brand we use, looks identical to what we fit). We regularly just replace the unit and reuse the mount plate.
The bigger question mark is about the status/condition of the fixed wiring, but the unit should have a test button on it.
Thanks, i bought 2 from screwfix for £20 each and they slotted in perfectly. Got no concerns on the wiring, the previous owner of this house was a perfectionist, the smoke alarms have their own dedicated labelled circuit on the consumer unit
Looks like a standard Aico base (I think that's the brand we use, looks identical to what we fit). We regularly just replace the unit and reuse the mount plate.
The bigger question mark is about the status/condition of the fixed wiring, but the unit should have a test button on it.