Alarm nightmare

Help!! my house alarm is beeping annoyingly and flashing trouble at the control panel.
We don't have any code as the previous owners were in a contract with British (RIP off ) Gas.
Was thinking I all just get a new control panel fitted but cant afford atthe mo, so to stop the annoying beeping I disconnected the backup battery and removed the fuse next to the system box. This shutdown the control panel but the Alarm was still sounding on the outside of the, house cant understand where the power is coming from to do this.
I feel like doing a Basil Faulty and smashing it to pieces with a hammer
Any advice much appreciated.
Will

Bell has its own battery and should stop after 15 minutes or so.

This is correct function.

Cheers mate ...I should get a good night's sleep tonight

I gather you bought the alarm system along with other fixtures and fittings. One thas doesn't work because the previous owners won't give you the code, why? You need to use it until you are in a position to get it set up as you require, I don't really see the problem