Did you badger the spark to install the system because he was cheaper than a fire alarm company? People ask me to do all the donkey work pulling in data cables and stuff for other people all the time, ok I'll graft my arse off pulling in all your cables and you turn up in a suit and tie, program it all and make 10 times as much as me, I don't think so.
This sounds like a typical installation that ends up with holes everywhere, chancers wired the fire alarm in a star configuration but probably daisy chained the network cables, don't you just love em.
Reminds me of a job we did last year, a 7 bed HMO, we priced for the electrics, emergency lights and fire alarm, we only got the electrics part as he had a mate "that could do fire alarms". I was there whilst he was installing it and I thought it was all a bit strange, he looped a piece of 4 core FP cable in and out of every point but it just ended up as a radial at the furthest away point ,no loop, no separate circuits, just one big radial. When it was finished he had just put a load of Aico smoke detectors at every point, no fire panel just domestic smokes. Not sure how that has gone down with the council/licencing body, I thought a HMO had to have a proper fire alarm system, I priced for an addressable system at about £5k. Also I still don't think he ever connected the emergency lights or the smoke detectors to the mains, he must have assumed I was going to do it for some odd reason.