Help advise Req'd 1999 UK2000 ABS/ALARM/IMMOBILISER/ECU PROBLEMS.
 

I just nipped to the bank, on the way back, pulling off The ABS light stayed on for more than 10 seconds then went off, when I nailed it, this never usually happens. When i got home the alarm went hay wire when I turned the engine off, The key on the dash board started flashing. The other flashing lights started then a fast ticking stated coming from the drivers door and under the dashboard near the fuse box. the alarm keeps going loud then quiet. the lights on the dash board came on but very faint, Then came on full brightness, then faded, I kept hitting the phob, the hazards flashed I tryed starting it then it ticked and the alarm stayed going off again. I typed in the override code but nothing. The immobilser turned off, the alarms seems to be going loud then quiet. I have checked the fuses they appear to be ok.. what could be the problem.I hope it doesnt relate to fitting new full st st exhaust system, turbo and panel filter

I have just disconnected the battery. Will leave it over night. as its annoying the neighbours.
Could this be a ECU Problem. can any one advise what I could do to sort it out?