Can anyone identify this?

[Markiii]

Working behind the trim panel on the left hand side of the boot and came across this little lot.

Can anyone tell me what it is?

[MikkiJayne]

Central locking pump in the foam, alarm module underneath it with the red connector

[Markiii]

thanks MJ that explains why I heard a random whir when i had my head in there

[HPsauce]

And the alarm horn is behind the curved metal panel above the pump unit.
It's secured by that nut you can see on the protruding bolt which IIRC has a head that slides into a slot in the horn, or it may be moulded into it?