Dave Plowman wrote:

you might have problems getting a cabled alarm installed to the
same standards as decent DIY. Like concealing all the cables.
Yep, I installed the cables at various times when I had floors up,
ceilings down, was building stud walls, replacing coving, or installing
PVC doors (magnets and reed switches hidden within the doors/frames).

A couple of drops required chasing a slot and re-plastering, the only
visible cabling is within the garage and shed.