peugeot 306 electrical problem?

one afternoon when returning home, the engine wouldn't turn off, the dashboard stop, oil and battery light remained glowing slightly, even after the key was removed and the engine was deliberately stalled. At this stage, alarm and central locking are working perfectly. As i have a small amount of knowledge of vehicles, i diagnosed a key switch fault as the solonoid had a continuous supply of power. we replaced the key switch and it's still the same fault. we looked at our haynes manual for the fuse list, no remedy for this fault was listed, so i started to randomly remove relays and fuses to see what happened. fuse 15 killed the engine at this stage, we also found the alarm and the central locking was disabled as far as the key remote was concerned, although use of the key in the lock works the central locking perfectly. according to the haynes manual, the alarm control unit is fuse 26 (this does nothing). Fuse 15 should kill the central locking control unit, remote control unit, courtesy lights, boot light and electric aerial, although fuse 15 being out does not disable the central locking and my boot light still works.
WEIRD

PLEASE HELP