A good few times, we are in the trade and are on call 24 hours for this type of thing.
Could you get somebody to respond to your system within 4 hours 24/7 365 and repair it?
https://www.nsi.org.uk/information-centre/information-for-businesses/police-policy
999 an alarm system in this way is against regulations no matter how much value for money you think it is.
Personally I see it no better than a speech dialler, which has no subscription fees and less to go wrong.