Check the wiring u may be lucky and each detector may be wired back individually to the panel. If not easiest option guna be to use what wiring you can and replace rest with wireless
Just twist the blue and yellow at the kitchen pir and wire the hall with the blue and yellow i reckon that will work. Wrt the bell does it have the tamper switch with the circle base that goes at top left or is it the old style to the bottom left of the pcb ?
I think i worded that wrong lol, with them joined together in the kitchen do u get continuity on the cable from the panel to the hall? U can actually wire each detector with 3 cores if u link 0v and com in the detector, then wire the other core to eol terminal on the panel