Same for Cheshire too, we did have the same chief for a while tho
Hopefully they will last a bit longer. Here in Manchester the fire brigade will check any alarms you already have fitted anyway and ensure that they work or replace them.
When i moved into my new flat I fitted a bunch of those Fire Angel alarms as they were advertised that they had a 10 year life, even on the back of the alarms they give you a date to replace them (the date on all my alarms was 2026) which is around 10 years minus the time they have been sitting in a shop I guess. Needless to say they didn't even last 3 years.. and as you said they have built in batteries so you cant replace them.
Excellent I hope people take it up.
If you live in Mid & West Wales, please fill in the form via the below link, to request a Home Fire Safety Check. (y) http://ols.mawwfire.gov.uk:8059/onlineservices/homevisitrequest