[Closed] Standalone garage alarm on a timer - does it exist?

This has probably been asked before, but I can't find anything on search (both STW and Google) and may have a unique twist anyway. So, disclaimer over, here goes....

I'm looking to install a standalone alarm system for the garage to protect all the nice shiny (mostly dirty) bikes and stuff in there.
The garage is on the other side of a shared parking area to the house about 20m away from the rear of the house. It has mains power and lighting.

What I'm looking for is a small alarm system, probably door open magenet activated rather than movement sensors. There is only the up and over main door, no other access.
However, I'd like to be able to set it on a timer so that it activates overnight, say 10pm to 7am.
I'm guessing that if I simply stick a basic socket timer on a plug-in alarm then all hell will break loose when it switches the power off while activated and wakes the neighbours at 7am every morning! 😳
Also, would it reactivate when power comes back on?

So, is there a unit out there somewhere with such a built in timer function that I can plug in to mains? Or hard wire is necessary, or battery if the battery life is decent and I won't be spending hundreds a year on batteries!