I’m after a kit with a wireless pad (to be put in the house), a LOUD sounder, a pet friendly PIR sensor and maybe a door contact. Only need a single zone. The house has an ADT alarm (honeywell panels) but it’s discontinued and I can’t find any info on what I can do with it. A standalone would probably be better anyway.
Anything to stay away from? No closed protocols please!
Hoping to grab something for around £100, is it easier/affordable to buy a panel, sensors and sounder separately?
Recommendations appreciated!

I got a Yale wireless alarm system for about that. 2xPIR and 2 x door sensors. All battery powered with a 5 year guarantee on life. My garage is 50ft from the house and the sounder is loud enough to wake me.
It came from Screwfix and installation was very easy.

I looked at that one Steve 6200 or similar?

Yes that’s the one and only £80 at homebase at the minute it seems.

those yale ones used to come with keyfobs rather than a remote pad – not sure what the range was – but they weren’t bad

I fit quite a few alarms and I always get them from Alert Electrical.
Cheapest place I’ve found.

link