SI-601 Ionisation Smoke Alarm only £5.76 at Plumbcenter
Over £11 on Amazon.
They have a few good offers at the moment in their January sale.
The battery is replaceable in this device and the picture on their webpage is the wrong model!
Free Reserve and collect from your local branch.
There is also a good offer on the S0-601 Optical alarm (toast) at £9.17.
Top marks goes to the HT-630 Heat alarm though at only £6.06.
20% discount for your 1st order !